55-57 Passenger cars and 3100 TF trucks with a 3 speed or OD trans use the same driveshaft. I believe the earlier models like your truck have the same wheelbase. If so, find one for those years and you don't have to make one up.

Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine