Welcome to stovebolt. The standard rear for 1938 was 5.33 I would expect your 36 was similarly low so they will run 55 but are screaming. You have a enclosed driveline. to switch rears you would be looking at changing transmission, drive shaft and rear end. If you are looking at a engine swap later trucks used different engine mounts so you may have to look at modifications there as well. Some later bell housings are not compatible with the pedal set up in the 30's trucks, they can be tapped so you can mount the pedals as they are currently mounted in your truck. Water pump location can be a issue when doing a engine change they do make adaptor plates to properly relocate water pump.. Not sure what the 206 shares with the later 216 I have but I would guess it has babbitted instead of insert bearings, slinger and oil pump lube system with a trough with a drain in the rear main bearing cap back to sump instead of a seal. A lot depends on your skills or depth of your pockets. Mike's suggestion of moving sheet metal to a modern chassis may suit your goal of highway friendly better than modifying existing drive train.
Last edited by kb3csw; 04/24/2019 2:14 AM.
