Would a Chevy 305 bolt up to 1940 Buick 3 speed manual transmission and bellhousing?
No, a Chevy 305 small-block V8 will almost certainly not bolt up to a 1940 Buick 3-speed manual transmission and bellhousing. The bolt patterns on the engine and transmission are completely different. Even if you could somehow adapt the bellhousing, the input shaft on the Buick transmission would not match the Chevy engine's clutch setup. It would require a significant and likely impractical amount of custom fabrication.