Postal Jeep head

A gave me a rebuildable head from a DJ today along with the intake and exhaust manifolds. He says the parts are all off the same engine and are original. The intake casting date is 11/78 and I haven't found the numbers or date on the head yet. The head bolts are 3/8", same as my cuurent head. He said the engine was a 232.
The thing is, he gave it away before and the guy brought it back because something didn't fit. An air conditioner bracket or something to that affect. My understanding was that that head should fit my '74 258 but this little mystery has me curious.
I measured as much as I could and will pull my valve cover off to check some more. Does anyone have any idea what the difference could be between the two heads ? So far it's just dirty with no visible cracks or warpage.

 

A 232 and 258 head will be the same in the same year. However, AMC used several different pushrod lengths and at least 3 different valvetrain designs with the 258 (early stamped rockers, cast rockers ca 1974, later stamped rockers). You need to use the style of valvetrain that goes with the head.

There are two different head bolt sizes, 7/16" and 1/2". Never heard of 3/8" head bolts - they would be too small. You can use a 1/2" bolt head on a 7/16" block using sleeves that are available from HESCO IIRC. A 7/16" bolt head can be used on a 1/2" bolt block by enlarging the holes in the head (I'd do it with a drill press, but a machine shop could do it trivially).

The Postal head may not be drilled and tapped for the AC bracket. Compare the mounting holes you need for your accessories.

 

Question - why would you rebuild this head instead of the one that's on your Jeep now?

 

I guess my eyeball estimate on the bolt size was off by a 1/16". The rockers are still on and they are different than the '74.
So I need the replcement rockers and push rod for a "78 are probably different too.
Around here it pays to have a spare head. We get pretty warm in the summers and I have always kept a spare head when possible. I always upgrade the cooling system also. A spare minimizes down time when something happens.