shmkr,
I have a 1940 truck, 1960 235, 198X T-5 and a 1955 1st series rearend. I changed the bellhousing to one from buffalo enterprises so I could retain my brake and clutch pedals, The 1955 1st series rearend is a direct replacement for your rearend but it is open drive instead of torque tube. This axle is a couple inches wider than the original but it was an easy swap. I also switched to monoleaf springs. I did have to monkey around with the emergency brake cables to make the 1940 cable work with the 1955 rearend.
I didn't know about the pumpkin switch or I would have done that. The tricky part of that switch is changing the spring perches as mentioned above. The torque tube rearend's perches are designed to allow the rearend to rotate as it goes through the suspension travel. Not something you want with an open drive line.
Good luck with the swap.
