man.....
if you're sticking w/ only factory available stuff.....
I don't know how you could be choosing ANY chevy motor and it NOT be the new LS7......it weighs less than your 4.3, makes better than twice the power, and is factory dry-sump'd......come AWN....
from there....I dunno.....nv4500-203/205.......simple/easy/strong...
there's some other combo's I'd love to afford to try out that I'm sure could work really sweet...
the newer 5.4's in the Lightning's really get-it, and have a hell of a bottom end.....one of those in front of its factory auto tranny, in front of a 203/205 would be a helluva combo in something 3500-5000 lbs....(toy, scout, lwb jeep thing)
and, I've always wanted to get an old skool taurus SHO motor in front of some fast-close ratio 5 speed, in front of something like a D300 or Toy case and put it in my Samurai......that would scream in the sand.....
(or just a short-star $$$$$)
--B