Post 1950 Buicks used "insert" bearings. Before that (1948-49) some had
insert mains with rabbit rod bearing surfaces.... others didn't. So, stay clear of the pre 1950 motors for your project.
Also Buick made two sizes of straight 8 ...263 (Specials and Supers) and 320 (Roadmasters) cubic inches.
I'd probably opt for a post 1950 320. Either way, you'll need to deal with the Buick "torque tube" issue in your drive train. Maybe a stick set up with an old style trans adapter for Ford or later GM? Most Roadmasters were Dynaflows by 1950.
I believe you could also get an optional 4BBL carb on the big straight 8 in 52 (maybe 53), but I'm sure these parts would be pricey.
