I dont know if this will help,but when I built my 36 Pontiac, I found out that a 55 or later pickup 3rd member will bolt right in. All I had to do was change the axle gears to match the Pontiac axles. I even used the original brakes because they were slightly wider than the 55 brakes. As far as using the 5 speed trans, I only had to space the trans from the bell housing using a couple 1/2” washers
In between the bell housing &trans. You will need to drill out the mounting holes to 1/2”. Hope this helps. Joe