You can get away with very *little* fabrication.
Motor bolts right in..
headers - fit other than if you use 2000 accessories... even then, a cut and couple welds on the crossover makes it fit.
Talk to McCoy, he has a 98 or something RWD S10 with a stock block & crank big buildup (Vortecs, mild cam, FAST). Just ran 12.0 @ 120 on a very conservatively tuned 15psi. First track run on the truck, fresh motor.
With the 18s you'll need to completely fab headers, and you should really run a *big* cam to match the heads.
I'm trying to make your life easier, I've been down that fabricate everything road... it is no fun unless you do this work for a living and you want a *very* unique vehicle. As it is, your truck will be unique.
It's all your call obviously, I just try to steer people clear of PITA ideas...