Which Tremec since T5 bit it?

[Mad Horse]

Hey guys, driving down to Dayton, OH on I75 today when all of a sudden my T5 started rattling like a bolt in a coffee can. Drove her softly to Ford staying out of 5th gear cause it sounded horrible and had the trans man take a ride with me. Anyways, I'm assumming it isn't worth the money to rebuild and Ford offers a rebuilt T5 for 1600. Since I can get a Tremec for this price I think I'll go with that instead. I might let them look at it first and see what it will cost to rebuild. If it is too much I'll go with a Tremec. Which one though? Is there one with more of an OD? I would love to reduce my RPM's in 5th gear since it sees a lot of daily driving with the 3.73 gears. Is .64 or .68 more of an OD? Confused on the tranny gear ratio thing. Tremec doesn't make a 6 speed for the 5.0 do they? Any suggestions? The car goes in tom. for inspection so I need to decide quickly.