the difference between your rice motors and an SBC is the number of valves.... multiple small valves are more efficient than single large valves... thats the one drawback of using old design engines is there are some newer designs that just cant be implemented.... i guess someone could make an aftermarket block to add valves to an aftermarket head... but you would have 32 pushrods and 32 lifters and 32 cam lobs.... thats a lot of somethin to go wrong....... its a lot easier to work these designs with an overhead cam... which i guess someone could make an setup to run an overhead cam on an older v8... such as the ford 427 cammer