Brian,
It must be eazier to use an adapter plate on your bellhousing and retain the pedal mounts. The t-5 has a longer input shaft which makes extra work in trying to adapt it without an adapter plate. Cavebull and Steppinwood both have excellent photo documentation of this conversion.
I also have a 1940 (GMC) I had an adapter plate made for me out of 6066 aluminum at a local machine shop. It is a relatively simple job. I will be using a NV4500 transmission instead of a t-5. In hind sight the T-5 seems like a more appropriate swap. The NV4500 is much bigger and wider than the stock transmission and the t-5. I still might have to come up with a system for mounting the clutch and brake pedals.
The advantages of the NV4500 are it is stronger, it has the same splines as a stock transmission, it was new, it has both a granny low gear and an overdrive. Disadvantages include the size and the cost.
