Thanks for the info. Ya I have done the 4.0 swap on my Gremlin. On Oct 6, 2010, at 8:23 PM, Sandwich Maker wrote: " From: RAY MICK <rmick@xxxxxxx> " " Anyone know which 4.0 cylinder head casting number works best for " installing on 258? Wanting to install a 4.0 head onto my 81 S/X4. they all work well for that, but most often used are the early '90s 7120 or late '90s 0630, as they line up with the early '90s obd1 efi that was the base for mopar's retrofit kit. looking the other way, '87-'90 258s are the best for 4.0 head swaps as they have the same wide deck - no water passage doctoring - and went back to 1/2" head bolts. next best would probably be '70s 258s, which also have 1/2" head bolts, and cylinder walls thick enough for 4.0 slugs. '81-6 258s have 7/16" bolts and water passage mismatch to deal with. why not swap an entire 4.0? you wouldn't be the first... ________________________________________________________________________ Andrew Hay the genius nature internet rambler is to see what all have seen adh@xxxxxxxxxxxxxxxxx and think what none thought _______________________________________________ AMC-list mailing list AMC-list@xxxxxxxxxxxx http://list.amc-list.com/listinfo.cgi/amc-list-amc-list.com Ray Mick The older I get the faster I was. Somewhere in Kansas See my AMC's @ http://members.cox.net/kamick1/Site_2/My_Space.html www.midamericaamc.com _______________________________________________ AMC-list mailing list AMC-list@xxxxxxxxxxxx http://list.amc-list.com/listinfo.cgi/amc-list-amc-list.com