Making progress now - parts coming in...etc.
Found some cool info from a truck site that did a 8.1 swap:
Unless you work at the Tonawanda, New York, assembly plant, this is probably the first time you've ever seen the new Vortec 8.1L (that's 496 very nasty cubic inches) big-block on an engine hoist. This one came to us directly from Chevrolet, but it's rumored a GEN VI crate engine from GM Performance Parts is in the works. In the factory HD truck trim these mills produce 340 hp and 455 lb-ft, but in our nonemissions marine trim (no smog pump, no EGR, a set of headers, and a trick new EFI controller) it puts out an estimated 420 hp and 505 lb-ft of torque.
And...on the flywheel/trans:
More good news. The 8.1L is internally balanced and will accept the old 14-inch, 168-tooth, neutral balance flexplate from a 396 or 427. Just don't try to run an externally balanced (weighted) flexplate from a 454 as it will damage the 8.1L's reciprocating assembly.
And...on fitting it in an older or even an LS application:
It gets even better. Even though GM has adopted a new engine-mount location on the new Silverado chassis, the old GM engine-mount pad is still cast into the 8.1L blocks. Want to bolt an 8.1L in where a 454 came out? No problem
Source:
http://www.4wheeloffroad.com/brandpa...t_1/index.html