Avery4jc said:If those are your options your thinking of right now I would stay away from TCI, everyone I've talked to has said that they are great when they work but when they don't they are a pain in the rear for support.
Someone else to think about is www.maddogtransmissions.com
he seems pretty cool too.
-Avery
man, those trannys seem pretty beefy and they are cheaper than the others...
can someone who knows alot bout trannys (i know next to nothing bout them
) please look at the godfather and punisher 700r4 from maddog and tell me if those are nice components. id really appreciate it
Well you've got plenty of gears for 39.5's so I would be inclined to say go w/ an NV4500. The SM465's first gear is super low but you already have the gears to get moving so that isn't an issue (although it's a plus to the SM465 for those of us that don't have low enough gears) so I'd say go NV4500 since it will give you similar performance to your 700r4 but it'll handle a heck of a lot more.
As far as first being useless....haha now thats pretty funny.... 
Thanks for taking things so literally. He knows what I meant.
the cost was just too great. You could drop in a bb454 or even a Caddy 500+cid engine and a killer 4L80E w/ stand alone computer for much less than a bone stock duramax/allison combo. I took a ride in my dad's shop truck, a bare bones, (no carpet, cd, power anything) 2500hd w/ the duramax and allison combo and let me tell you what that thing would move!