I put a WC T5Z in 1801 back in 2006. I worked with Bruce at Modern Driveline. There were a couple of back & forths but he worked through them with me quite satisfactorily. To begin with, I have a COBRA scattershield and the first adapter plate did not line up (bolt pattern). Bruce got me a different one and it was spot on. I used his cross member and shifter assembly and did not need any modifications to the tunnel or bodywork. The driveshaft did need to be shortened, but rather than modify my original, I worked with a local shop and we just built and balanced a new one. It is not a very expensive project and I have the original setup intact, if I go back to the T-10. As a sidenote on the driveshaft - when I changed my gears from 3.89 to 3.50, 2 years ago, I put in a complete 3rd member and needed to alter the driveshaft again (there's another learning experience on pinion & universal sizing). Once again it was cheaper and easier to have a new driveshaft built and balanced than to modify.
Of all the changes I have made, the T5Z is no doubt the most useful. Last spring we drove down the Blue Ridge Parkway to the Tail of the Dragon. It was 1800 miles and seven states in 10 days, and after the run, just being able to cruise home on the interstate was worth the price of admission.