i ran around on a stock 6.0 with a stock 4L60e.. no issues... when i put a cam in it and got it tuned.. is when it went POP....

i had a buddy with a radix 5.3 and i had a stock Lq4 and we ran right around the same 1/4 mile... but i had a few more supporting mods..

either way you want be disappointed... the 6L probably will be cheaper.. and as far as a converter.... a 2K with that 2.5 first gear in an 80e is gonna suck

get some more power and it wont bog as much