I've said this before, but I think that the T-5/250 combination is about perfect. You'll have another gear for around town and the OD 5th for the highway. Your 3.73 should be great!
Try to find a good '87 back transmission because they have the mechanical speedo cable fitting and will not need an expensive adapter to work with your truck. The best T-5s for your truck are found in S-10s as Wrenchbender Ret. says.
good luck and best wishes,
Les
