A couple of us have been down that road. I used the stock manifolds and clearanced the frame in the offending areas. Nothing major. I don't have a pic of that area on my photocket site (link in sig) but I'll try to put something up soon. I've been told that LS1 F-body manfolds hug the block closer and are not as much a problem as the truck manifolds. Haven't seen a set installed on a ROBS truck however.

BTW, welcome to the board!