In 1948ish, the transmission bellhousing mounting pattern changed. You should be looking for a 1948ish to 1954 chevy or gmc 6 cylinder bellhousing. The rear engine mounts would be the same for your stock application. All of the parts suppliers like Jim Carter or the filling station, or many ohers should have them in stock ready to ship.
If you are using a 1955-1962 bellhousing with the "angled" mounts, you will need to make or modify a crossmember to take the 1955 and later motor mounts. It may be possible to source a crossmember from a 1955.1 truck, or simply weld in a later crossmember.
