For your application in the 1 1/2 ton, you need all the low end torque you can get and thats what the 261 will give you. You want to find a machine shop that knows these old motors and that is becoming more difficult each day as the grey beards are retiring.
There are several issues you want to make sure are addressed with your engine build: cam(stock 261 was a good one and can be reground), rear main/rope seal must be done right, modify the block for modern full flow filter(see tech tips), keep the original 261 rods, use 235 head that casting #ends in 848 for a bit more compression. Plus several other details like aluminum timing gear vs fiber. So you can see that you must do some research to get the best engine job you can. Read everything on this site re. motor and also check inliners.org site for more info. You can also do several things to make life easier like going to 12 volt electrical, modern distributor/electronic, NOS or modern carburetor etc. BTW I kept original bellhousing, flywheel/clutch and starter in my 46, 6 volt starters love 12 volts.
As stated, keep your original bell housing and front motor mount plate, all bolts right on.
All 216/235/261 distributors will fit but I like the later 12 volt units as the points are easier to find and Pertonix makes a kit (#1166) for that one. Also you can modify the later inlines HEI unit to fit your motor.
