Brian -
I just completed the installation of a T-5 in my 37 pickup.
I would highly suggest you go the adapter plate route. It is much easier - you won't have to shorten the transmission input shaft and you won't have to lengthen the splines on the input shaft. Mine worked out great! The one thing I don't like about the later bell housing is the fact that the mounts have to be welded on for the brake-clutch pedal and master cylinder bracket. I have never been comfortable with welding cast iron, especialy steel to cast iron and when it comes to the brakes and clutch, I would try to avoid this sort of welding activity. I think you are much, much better off with the original bell housing and the use of an adapter plate.
Of all the advantages, the biggest is that you wouldn't have to pull the bell housing from your truck, a job that I see as a pretty good size chore. Probably the easiest way to pull the bell housing would be to pull the engine, which to me means pulling the front sheet metal. Allot of work to avoid a safe and sensible transmission adapter plate.
Just my 2 sense!
Good luck,
Joe
