greybeard,
the pontiac sd head will bolt on and 2 can be made into 1 inline 6 head. those are as rare as hens teeth and expensive. still need custom intake and exhaust.
the ls heads are cheap, plentiful and flow air like crazy. still need a custom intake, exhaust, side cover and block deck work and a custom cam.
i am still rolling over the idea. exhaust on drivers side, intake on passenger.
another problem is the water flow. these heads are designed as reverse flow. water to head then thru block. any ideas to keep it that way. of couse the inline way will work the easiest. tom
