It's kind of scary what some people put together. What you have is a passenger car stick shift bellhousing of the same era as the engine with the original trans. It's not an auto trans bellhousing. The mounting holes are in a different location on the early vs late so they just made do. There are number of members here with early trucks with your combo or V-8's that should be able to assist you. It's going to take some work but will be worth it in the long run.
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