Thanks guys. I was misinformed by NAPA on the bore size of the truck master. They reported 7.75mm and the Fbody at .75 in. Turns out on further investigation the truck is actually 11/16. So, it has just a little more stroke than the Fbody and 1/16" smaller bore. It'll be interesting with the internal slave from the LS1's T56, but I'm feeling more confident about it. Thanks again for the feedback. I'm surprised I'm not seeing more LS1-T56-based trucks.

How much futher back is the T56 shifter from stock in your trucks (my truck was 305/5spd)?
-gl18rider