If you're going to go thru the trouble of swapping engines, going LS is almost a no brainer. Newer technology, better efficiency, reliability, the list goes on. Even just having OBD2 is a big bonus. I've been down the road of building tbi 383's, or cammed 350's with vortec heads blah blah and would never do it again.
The time and money you would save from trying to turn a stock 195hp tbi350 into a 3-350hp tbi 350 compared to dropping in a junkyard 5.3 thats going to get better mileage and all around run better and have pretty much 300hp stock, is reason enough for me to do it. But these are just my views and opinion from having gone through it all back in the day. And for the love of god, don't go carbed.
I'll wait here for L31express to preach torque #'s