i have a 3550 tremec, and have beat on it with about 460 hp for over 60,000 miles, so i would suggest a tremec, but don't feel you need the extra strength of the TKO, as your tires will protect you with slip. By the way, i believe that the TKO has a stronger input shaft, but most of the internals are the same as in the 3550, such as synchro's, etc. Put the few hundred saved into a billet flywheel, perhaps. You may want to consider the 3560, i believe it has a different fifth gear, i believe something like a .80, instead of the .68 of the 3550. If you want to play with gearing and mph and stuff, why don't you run Mike Stenhouse's gearing calculator on the Second Strike website, check out:
www.secondstrike.com , then go to the gearing calculator.
We have not meant to ignore you, i guess we were all waiting for someone else to offer an opinion on what at least to me seems like a pretty easy decision.
Let us know if you want any impressions, we will try to do better.
all the best...