I did not trust the welds on those Chinese plates so I made my own from angle iron.
Fist off, NICE DELRIN FUEL LOG! Where'd ya' get that idea form?
The angle iron that you used will hold up a 10 story building. The issue, IF there is one, is that you are lifting 500 pounds on 5/16" soft steel studs on an aluminum casting which really isn't designed for that. An iron intake would do much better.
There have been many that pull an engine this way so it obviously is safe, so why not? Personally, I've never done it that way.
Looking at how the factory lift brackets are attached into the heads with even in the case of a 650 pound FE with a single 3/8" bolt into each head, that one looks worrysome as well but is a piece of cake other then you are leaning on the sides of the valve covers.
I like to bolt up to the bellhousing and one of the accessory bolt holes in the heads like for the alternator, etc. and use the balancer to aim the the engine in.
Don't forget that if you are pulling out the transmission bolted up, that's another 300 pounds, so with an FE, that's 1,000 pounds to reach over with the hoist with.
Coming out is not so much of an issue, threading the needle back in is another issue, but that's not for today, that's for tomorrow.
Try this in a Pantera with about 1/2" to spare. It's challenging and the engine goes in only one way and you need to find it.