I can't tell you how Scott built his, but the stock bellhousing in your '66 will bolt to the big block. A 454 is externally balanced, meaning you have to use the 454 flywheel for it, but the other big blocks are internally balanced, so your original flywheel should work.
The stock V-8 mounts for a '66 should mount the big block just fine. If its a six, know that the 230/250 mount differently than a 292. The mounts may be the same, but only need to be moved, but I'm not sure about that.
Years ago I ran a mildly modified 350 in a '70 4x4 Blazer. I drove like a kid in those days (probably because I was one) and broke the transfer case twice and destroyed the front drive shaft once.
I abused that truck a lot, and it would break...
