Whould be sad to see the '29 with a newer engine...that was the first year for the 6-cylinders and they made changes every year until the 216 came out in '37.
Bearing issues can be delt with and water jacket cracks can be fixed. The amount of time and money you spend putting the '31 engine in you might spend the same and keep the '29...worth looking into.
Have you talked to any of the guys at VCCA? Maybe place a block wanted ad there and see what turns up. The engine in the cars is the same as the trucks, so there's another source for help.
Mike B
