Try removing the alignment studs on both ends of the head and replacing them with 3/8" bolts a little over an inch long with the heads cut off. Once the manifold is installed, you can replace them with the short dowels if you cut a screwdriver slot in the short ones.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!