Should I keep the PCV in the valve cover, or install it in the "rear of the manifold" location, which is currently capped off?
The answer is: it depends! Aesthetics aside, although every engineering attempt should include this consideration, I would advise on an FE mounted in a modern Cobra to have two "open" breathers mounted, one to each valve cover, of a type with baffling consideration for resisting oil loss to the exterior, and the P.V.C. valve inserted into the rear intake manifold breather opening also with the required baffling to impede oil entry into this plumbing. Although this does provide a certain sum of symmetry, it's functional in that first as indicated previously the plumbing is routed uphill from the valve to the entry to the manifold which also as mentioned previously should be under the carburetor presenting particularly the oil contamination in the plenum area thereby dividing this sum among the cylinders and not the presentation into a singular inlet runner.
In this layout initially at idle and low engine revolutions with reduced load the air flow routing enters the crankcase thru the breathers mounted to the valve covers, being one in each cover increases the available area reducing the velocity and drawing or shall we say flushing the unappreciated by-products of combustion fume and water condensation from both internal sides of the engine toward the P.V.C. valves' central mounting. This presenting access to the crankcase thru the intake manifold valley cover is an area well shielded from oil throw-off from rapidly moving components. But understand not immune as we currently have a 427 T.P. mounted on our dyno in which the assembler (not us!) failed to install the gasket for sealing between the tin valley pan and intake, in short order of operation one has a swimming pool of oil accumulating on top of the cover pan.
As the engine increases in speed and load the blow-by sums greatly increase, soon to the point beyond the flow capacity of the P.C.V. plumbing and now these excessive sums are emitted from the "open" valve cover breathers, and this is the happening that creates the greatest incident of oil escapage and the point of need of typically as defined an "oil catch can". Again this makes for sound intention as with the area of two "open" breathers velocity is reduced (vs. having only one), and other than oil directly thrown up the pipe (evidence of poor baffling) it is this velocity rate that effects the weight of the oil carried in the air stream and thru the plumbing, and as not to nitpick terminology, your not actually "siphoning the pan dry" as in a straw stuck in you soda can. The breathers mounted high on the engine also aid in the separation of oil as the atmosphere being evacuated is emanating in path from lower in the crankcase where the heat and turbulence is greatest and the bulk of the mixing of the oil in the atmosphere takes place here and with the required lifting of this heavy mixture enroute to the valve cover mounted breathers much of the oil is permitted the opportunity to drop-out even before it becomes a concern for a reasonable attempt to baffle your breather system in an attempt to preclude the remainder escaping.
The P.V.C. valve installations' greatest perceived value, in your street driven Cobra, is to reduce the obnoxious fume emanating from the breathers, this generally noted particularly with the engine (oil) hot, and say when at idle stopped at a traffic light, this can even perhaps escalate to the point of presenting a not so pleasing cloud about your vehicle that may not only be odifferous but not present the best presentation for your vehicle. And yes, there is the benefit of "less" oil escapage and this rather messy presentation upon opening the hood, or if permitted even to the point of dripping on the ground, with the joking statements that your car is marking its' territory every were it's parked. But again in reality the bulk of the oil carry-over whether external or in the plumbing, particularly of the "closed" venting systems, takes place when your on the throttle, and this is beyond what a properly intentioned P.V.C. system is designed to cope with.
With a track car, I would eliminate the P.V.C. plumbing, then along with the valve cover breathers, utilize the rear manifold mounting for another crankcase breather outlet. If permitted reasonably baffled to open breathers work best; sometimes you just can't improve on simple! If plumbing to catch cans(s), as stated previously mount the reservoir(s) as high as possible, route the plumbing up-hill, particularly as closer to the point of the mountings on the engine (example: in the photo presented in reply #11, the driver side breather hose fitting is pointed in the worst way, down), and use the largest possible (reasonable) plumbing lines and fittings (again, (and he's going to hate me!) in reply #11, this is a minimal size hose in plumbing, but perhaps acceptable on a well sealed small block) as this reduces the velocity allowing the heavier oil mist to drop-out in the line, and if it's downhill to the valve cover, the oil will just drip back into the engine where it belongs. Its' best to be diligent at keeping the oil out of the plumbing rather than trying to figure out what to do with it once it's here.
The problem with most of these cute, billet "bling-bling" catch-cans is that they lack enough internal area to create the velocity reduction required to make them function, and not enough effort in the baffling to make up for this, but perhaps often incorporating something that looks like a filter element(?) which it is implied "separates" the oil from the atmosphere, which it will to some degree, or is it that with the restriction created by this element, particularly once saturated, oil that contacts it is rather infused back into the air stream? But we already have some previous statements made where they have found minimal remnants of anything, so how well is this working? Or, was it really needed to start with, so how good does it really need to be? And then if it were to capture any real volume they lack any capacity for storage, which further defeats their abilities. Also, if a track car with any great singular on track duration time intended, plumb the catch can canister drain back to the engine (oil pan?) as if you are "siphoning" the oil out of the engine, it will also be automatically flowing back in and not draining the pan.
Scott.