Kube
Super Moderator
I have installed a set of 48 gears in to a 33 gearbox withProbably your best bet would be to install '39-'48 passenger car gears in your '34 transmission case and use a double detent shifter top with the wide 2/3 fork. These gears will fit the early case while some of the pickup truck gears will not. This would give you the equivalent of a "39 transmission" while allowing you to retain the original serial numbered case.
wonderful drive-ability results.