The 850 head will bolt onto any 235 from 1954-62 as well as the 261. It will have a very slightly lower compression ratio than an 848, but it's still a good head. It can be milled to raise the compression ratio to the same as an 848 as long as the intake valves are recessed the same distance as the head is milled. The six coolant spray holes between the cylinder pairs will have no ill effects on a 235 block- - - -they just won't flow any coolant because the 235 block isn't drilled for them.

"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!