trans question

You are absolutely correct.

The input torque rating of the T-bird T-5 is lower than the one that would have been in that car from the factory. Also, the gearing is WAY lower, yes it is desireable, but 5th gear is practically useless, as it's not that much of a step up from 4th. Here is a chart showing the gear ratio's, input torque ratings and year info for the T-5's. Check out that T-Bird compared to the Mustang's.

http://www.therangerstation.com/T5ID.htm

There have been endless threads over putting a 4-cyl T-5 behind a 5.0, and yes it will work, i have a friend that has one in his '84 vert 5.0. But, they won't hold out forever, especailly behind even a lightly modded 5.0. Granted, an '85 5.0L H.O. doesn't have the power output of the '87 and up motors so the tranny won't suffer as much.