Just a note - for the cost of a hybird head + $800 one could get a 4200 vortec ($500 on ebay)- add race cams ($1200 - 1400),headers and an intake make 500HP all day long and not have the headache of trying to keep a hybird head sealed....
51 GMC 4.2 turbo Can't solved today's problems using the same technology/thinking that created them