I don’t recall seeing any new heads with inserts cut into them already – but to be honest, I don’t recall looking for that aspect. I can see factory rebuilt heads with new seats or a possible usable new head that wasn’t cast correctly, cut to have an insert installed so new part would be useable.
I was wondering, can you get me the part numbers on those boxes, please?
For car, pickup and van usage (’70-80’s), I think the cylinder heads were pretty much the same across the board – depending on emission usage.
That said, I have a pair of ’79 360 motor home heads which are weird. It uses huge spark plugs, 360 exhaust ports, 360 combustion chambers but 318 intake ports. I hadn’t measured the valves but appear to be the smaller 318 valves. To make it even more odd, it had a 360 4-bbl intake on it which had a huge step between the 318 head (intake) port and 360 intake. All the (’70-80’s) small blocks were made at either Windsor, Canada or Detroit Michigan (Mount Road) assembly plants (depending if to be installed into a Canadian or US made car) – except for most motor home engines which were built in Trenton Michigan.
Also, I have no idea if military spec engine parts are different - which might be part of the difference (me shrugs).
BudW