Mike,
That is definitly a hard question to answer. A 350 Vs. a 383?
I suggest you try here for answers to your 383 questions.
http://www.chevytalk.com/
As for new GM crate Engines. Ls-1 is only 320 Hp w/ 345 Lbs of torque. It seems to be little less than you had before. The fuel injection and weight advantage are nice and certainly worth considering. They are a bit pricey though.
I would also suggest a nice ZZ4 385 fast burn. I have heard nothing but praise for these engines. If you are looking for a little more performance you can change the cam to Hot Cam and rocker arms from 1.5 to 1.6. You are now in the 430 Hp. range @ 5,800 w/ 430 ft torque @ 4000.
If you perfer a touch more Hp, you may also consider a little more cam, say model 12370847 or 12480110.
You can view the engines at
www.paceparts.com
Good luck,
Bud