What do you think of this setup? sb400/700r4/.308

[Hazieview]

I now have a sb400/350th/.308 I am thinking abou replacing the transmisson with a 700r4 because my th350 is giving me problems. I put it in gear and the truck doesn't move. Sometimes it takes it a wall to actually go in gear so I think it has probably been hammered too much. I figured that with the sb400 I'll have plenty of torque like always but I have a quiter and more effiecient ride with the 700r4 because I'll be running lower rpms when cruising down the highway. Right now I can smoke that one rear tire no problem but it's getting to be less fun these days. I'd rather just make an everyday driver that still sounds good and will get down when I need/want it too. Figured it would be less strain on my engine as well. However I just hope I dont destroy the trani or rearend with the kind of torque that sb400 can make. I'm planning on beefing it up a little but right now it just has a performer intake and a small rv cam. Sooooo.....

What do you guys think?