Promotion t45 or t-56?

so i have a thread going over in the tech section about a leak and it appears there's no sense in fixing the cause because it would be too pricey and I may as well upgrade. I'm an auto right now but want to do a conversion. I jut put on a paxton 1000 yesterday and head to the dyno tomorrow, probably keep it safe around 400 rwhp but will be upgrading to a stroker and forged stuff in the next few months and who knows what else, so I need a tranny that will hold some good power.

I was looking at this http://cgi.ebay.com/ebaymotors/PROM...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

But i noticed that alot of you guys run the t-56 they all seem to run around 3k, meaning it would cost a heck of alot more. The extra gear doesn't seem like a big deal either.

Can someone give me a real why I should or shouldn't shell out the extra $1200 or so for the t56. I just see that both will hold the power I'm wanting to run and figure the promotion is the better buy. am I wrong?

what do those cobra trannys hold?

I found a used one with 34000 miles and a fresh fidanza billet flywheel, spec stage 3+ clutch and 26 spline liberty input shaft. clutch quadrant, wiring harness, stock clutch cable

Would this be a decent set up? what else would I need? Would the bellhousing on this unit work or would I need a different one? What about a driveshaft?

thanks for all the help, I'm not finding too much searching.

thanks for the help saleen. I take it you've done this?

I've looked and looked but Im not finding too much seaching yet. Will the bellhousing work or will i need to buy new? I know i will need a driveshaft, but what else would I need to provide the shop with that I will be having do the conversion?