Yes... be REALLY sure that you aren't just losing water somewhere else.... it's a lot of work compared to just 2 jubilees and a new hose
Check for high pressure leaks -get the engine FULLY up to running temperature, and go hunting.
ALL hoses, inc heater etc.
Look for crusty deposits on the radiator -this oftens hides a leak as the water evaporates so fast you don't notice.
Same goes for the heater -check the tap on the back of the block, these can leak from a couple of places.....
Check radiator and block drains.
Then think about taking the head off
It is a very simple operation tbh, exhaust off, carb off, top hose, heater hose, oil feed to head, rocker cover off, undo all the headbolts and it's loose. The head is VERY heavy if you leave the exhaust manifold in place (probably a 2 person job to get it up and over the wing/radiator), but through bitter experience it is better to leave it on unless you are getting it machined -studs love to snap... and I even managed to crack a manifold into two pieces just doing it back up once....
Follow a Haynes, and you should be OK.
Unless your existing head is broken/worn out, then I don't see any point in swapping heads, if the other engine already has the head off then it would be worth comparing the two... other than that I wouldn't bother
*edit* nice looking truck btw