I'm familiar with the 4 speeds, and they will not come forward over the transmission cross-member without removing the cab.
(Removing the cab is not the easy way... but if you really want to leave a 4 speed on the engine that's the only way to get them out together, or torch the cross-member.)

Are the 3 speeds small enough to slip over the transmission cross-member? If so the radiator and support may need to come out first to make room?
Dropping the transmission still seems like the easy way to start.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-