If the current setup is shifting and braking well, let me offer a simpler fix. Make a couple of short brackets to bridge the gap between the bellhousing and the pedal linkage from fairly thick metal- - - -maybe 5/16" or even 3/8" thick, and use a flat washer or two to level things up and prevent putting any stress on the castings. That will reinforce the pedal mount and possibly avoid a disaster on a panic stop if something decides to break at exactly the wrong moment. Bracing what's already there and working will also avoid any further butchery of scarce parts.
If you decide to upgrade to a later model synchronized 4 speed transmission at some later date, a bellhousing change and possibly some modification to the torque tube setup might be required. For now, I'd recommend concentrating on getting the new engine installed and running, and avoid doing too many modifications at once. Floor shift conversion linkage is available for the 3 speed transmissions, but that would put the shifter at an awkward position and require cutting a hole in the floor pan. It would also require changing the rear end to one with an open driveline, not a torque tube.
Jerry
