I just converted my lt1 t56 to a ls1 t56. Research dude, i read over a hundred pages in forums before starting the swap. I think the ls1 t56 shifter is farther back from what i could tell, the bellhousing was longer on the ls1 style(not much at all though). I'll see if i can find some stuff for ya.
1999 silverado rcsb. 6.0L and. T-56, Hurst short throw, 4.11s, auburn limited slip, 3/4 drop, Nelson tuning, Texas Speed 233/239 .595"/.603" Camshaft, Kenwood everything, electric fans, custom made hood, custom tailgate, magnaflow 3 inch true duals, hooker headers, and too much money.
Soon- wheels and tires, Ford 9 inch with 5.13 gears.