Your rear crossmember will probably need to be removed. The bellhousing bolted to it and the trans did not have a mount. The earlier TF trucks have a similar configuration. You may be OK on the front mount from the 66. However, all the catalogues I have list a mount for 63-66, so I don't know what the differences are. You will need a rear crossmember for the 350 trans. These sould be available from a number of sources. My Truck Shop catalogue shows a crossmember for 63-72 but nothing for
60-62. You may need to get the 63 part and modify it.
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