Welp here's the latest news on my (not so) faithful Nissan Datsun 720 pickup.
It definitely blew the headgasket - as diagnosed by my dad. We spent about two weeks taking most of the truck apart just to get the cylinder head off to get to the gasket. Today we replaced it and put a new cylinder head on (the old one was warped beyond repair) and now we've hit another huge roadblock. After we put the valve rocker assembly onto the cylinder head we attempted to put the timing chain/camshaft sprocket back on, but it won't fit. We had a bloody hard enough job getting it off, now it won't go back on no matter how much we try. So now we also have to take the timing chain assembly apart to reset the tensioning piston and loosen the guide (which is far too tight).

Bloody thing! D:

I was hoping to have the truck up and running tomorrow before I go back to work, but now it won't be working until next week at the very earliest. :-/