The older OHV Ford engines started with the Y block ( 272, 292, 312 ) engines that I know of. The FE block ( 332, 352, 360, 390,406, 410, 427, and 428 ) engines. The Small block is the ( 221, 255, 260, 289, 302, Boss 302, 351W, 351C ) engines. The Big block ( 351M, 400M, 429, Boss 429, 460 ) engines. The 335 Series engines were the (351C, 351M, 400M ). The 385 Series engines were the ( 429, Boss 429, 460 ). The ( Boss 302, 351C ) had canted valves instead of inline vavles. Also the ( 351M, 400M, 429's, and 460 have canted valves. The The 351M, and 400M heads look like the 351C heads on the outside, but the have open chambers, and small ports like the 2BBL 351C heads. The 351C 2 and 4 BBL heads are marked with a 2 and 4 where the heads mate with the intake, where the Boss 302, 351M, and 400M heads have no markings. The SBF and the M engines share the same bore spacing, and you can use those heads on a Windsor engine using the Boss 302, or 351C style piston. You have to make sure you have the right Rod, piston, crank combo for it to have the right Deck clearance. If not the piston will either stick to far down in the block or stick to far out of the block. I've been messing with Ford engines since 1970, and I have alot of books on them. I like the 351W over the 289, and 302's because you can get close to 432 CI out of a stock block.