Could also be… and likely IMO… a warped head. This means that even after replacing the gasket, you will still have trouble. If this is the case, you will need to get the heads pulled and shaved. 
When I was an apprentice mechanic 12 years ago it was standard practice to skim (or shave, if you prefer) the mating surface of the head/s before refitting if there was any hint that it might have overheated at some point, the reasoning being that >90% of them were warped to some degree, and skimming made sure the gasket had a good surface to seal against.
Cost of a head skim: ~£25 at the time, probably a bit more nowadays.
Cost of taking it back off again if it leaks: £££s and at least another day until it’s fixed.
Are US engines different somehow? Different materials? Tolerances?
Tolerances and materials for a US engine are going to be very similar to UK ones, often now the engines are exactly the same, the only real difference is the we don’t use Lucas electronics, so our stuff works ( I Kid, really). My buddy has a Ford Transit, the only difference from one in the UK is that you would open the wrong door to drive it.
Capt
I’m just an idiot back yard mechanic, but 15 to 20 years ago the way everyone I knew did it was that if you pulled the head, the first thing you did was took it to a shop to have the heads “machined” (what you call “skimming” - some folks also call it “resurfacing” over here). It didn’t matter if we suspected overheating or not. The cost was pretty low, about $25 (U.S.) and if you didn’t do it you were certain to get yourself in trouble sooner or later, so we just did it every time regardless.
I don’t know if the pros did things the same way back then and I have no idea if they do it now or not.
We did in 1975, we do it today.
An ounce of prevention is worth more today than it ever was!
This is the correct way to do it today too. If you don’t, you risk blowing the new gasket in short order.
However, the cost of resurfacing isn’t that cheap. I guess the new alloy blocks and heads are trickier to resurface.
Sorry, nothing to report yet. Mechanic hasn’t called.
Sorry to not come back until now.
While I gave you my best info in my posts, I hadn’t done much other than listen to my son’s description of events. I didn’t test the fluid on the ground as I got involved in twilight.
Mechanic said-“I can’t find an oil leak. Main radiator hose was lose at clamp and radiator probably blew out all liquid. Sometimes old radiator fluid may mimic oil on the ground.”
So, Kid wasn’t at fault. All is well. I appreciate all the great info given in replies. They may come in handy in the future.