small block heads for a long distance cruiser

Are the 308 swirl port heads small port heads? Some of you guys have me thinking about a 318. If you use 308s they originally went on a 318, right? What kind of pistons would you need to get decent compression with them??? Would all the 318 rockers, pushrods and shafts work? Does someone sell rebuilt 308 heads?
No, 308 are pre magnum 360 heads