It may not be to involved, as the Toyota land cruiser folks seem to like the SM465 (a GM 4 speed that easliy fits your engine), so it's possible to go the other way.
Try these folks, either they have an answer or adapter, or should point you in the right direction:
http://www.advanceadapters.com/

What do you hope to gain from this swap?

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-