When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If you're running a ZF6 speed, either of the first two options would be good. The third engine will prove a little more work mating up the clutch/flywheel 'cause of the different bolt patter on the back of the crank due to the 2-piece rear main seal on the 400 block. Still 'do'able...just more work.
Personally, I'd build the 396 LT1. Lots of people have 383s. But a 396 SBC isn't quite as common, and has a nostalgic feel too.