Some of the later-model 305's had that offset bolt hole, but Goodson and several other rebuilders' supply vendors sell aadapter plates to convert those heads for use with either type of manifold. I bought one set of them, took some measurements, and now I make my own from 3/16" steel plate. Most of the manifolds have both sets of holes. It's the heads that have to be adapted.
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!