I agree with Wrenchbender....I'd hold off on a $600.00 box until you find you need one. I've purchased 5 used mid-80's NWC, mech speedo T5's...some .72's and also .63's from behind the 305 Camaros, running ATF and some running gear oil and I've yet to get one that was noisy or had synchronizer issues.
In spite of having what is considered a rather fragile case, I've hammered the .63's behind a built small block with absolutely no issues. I really don't understand how a box builder could do much of a "rebuild" for $600.00 with them furnishing the core transmission. The rebuild kits are about $300.00, a used rebuildable box $150-200.00 and add labor and $750-800/00 is a reasonable price. If you decide to go that direction I'd make sure he does more than just pop the top and check for synchro/gear damage.
The beauty of the T5 is that it's so darned light and you don't even have to run a cross-member so it's basically drop the driveshaft, pop out the shifter, disconnect the speedo, pop out the 4 transmission to bellhousing bolts and drop the box out. At about 75 pounds a determined guy can muscle a replacement box in solo.
The key is to MAKE SURE that you get your gearing/tire size dialed in to meet you own driving needs.
Dave
