Makes perfect sense if you're going to update the engine, to update the tranny, too.. especially if the new tranny has an extra forward gear, and the old tranny won't bolt right up to the new engine.
I'm in no way an expert, but i've personally sat in over 40 1941 thru 1946 1.5 and 2 ton trucks.. and every single one of 'em had that reverse lockout lever.
I would think an extra forward geer might help in the top speed department.. I can't imagine that trannys first gear is geared any lower than the stock trannys 1st.. which is really just a granny gear.
