T-5 from an 85 mustang

I am building a 66 coupe and plan on using a T-5 to replace my 3sp manual trans. I have access to a unit from an 85 GT. Is this trans a good choice for my mild 289 or would a unit from a diffrent year be better? Also to adapt the unit to the 289 do I need the bell housing from the 85 or do I use the one from the 3 speed.  

You can use either your bellhousing with an adaptor(from mustangs plus or others) or you can use the 85 bellhousing. The choice is what clutch linkage you want to use. With the later model you can use the cable clutch. If you use your present bellhousing you can keep your clutch linkage. The trans is a good choice, however that was the first year for the WC(world class) T-5 trans and it went thru constant upgrade until 93. So the later model trans is a little stronger. In any case you need to shorten your driveshaft and get a new mount and crossmember as well as a new yoke for the T-5. You will also likely find you will need a higher(numerical) rear gear with that trans.