I have an 88-95 one piece seal block,it came with flat tappet cam but the block has the provisions for roller hardware,lifter valley stands and cam retainer holes.Other than tapping these and getting the spider and related hardware is there anything else to do or be aware of?Thanks  

hopefully its a 350 and not a 305 measure the bore you might have a h.o. 305 they came in el cominos and camaros i think. someone told me that you can run the vertical bar rollers the ones you would use if it were an earlier block as well instead of getting the lifter valley spider i have the same motor and i cant find any internally balanced cranks for the 1 peice block you may have to use the two peice adapter to run an internally balanced crank  

I've got a '92 Silverado with a 350. What you've got is a truck block. See, GM started casting all blocks to be capable of running roller lifters (taller lifter bores), but only the car blocks got the spider retainer holes threaded.

I converted mine to a roller cam a few years back, and just went with aftermarket tie-bar style lifters. The advanateg to these is they're much lighter than the stock roller lifters, so you've got less stress on the pushrod/rocker arm/valvespring with the heavy weight of the OEM lifter.

On the internally balanced crank issue, The '87 and up 350s were internally balanced, and as far as I know so were the 305s. The only externally balanced small block that GM's ever produced was the 400.  

The 305 and 350 chevy engines with the one piece rear seal from 1986&up is externally balanced they use the same balancers as the internal balanced engines but have a counterweight on the flex plate.