How bad are they leaking?

I know it's kind of a hack fix but assuming these are new plugs perhaps a stopleak might cure it. Bar's Leaks has a good reputation for plugging leaks without plugging the rad/heater core.

If there is any rust scale left inside the block it could cure itself.

Either way it's got to be better than pulling the engine or K-frame. If it works, bonus thumbs. If not, well you were resigned to pulling the engine anyway and you're only out a few bucks for Bar's Leaks.

I was never a fan of rad caps much over 7 psi but I see you live close to the surface of the sun so perhaps it's a necessity.

If your system doesn't ever venture much over 200F tho I'd run 60% anti freeze in it which even at atmospheric pressure will boil 225-230F and with an 8 psi cap, 250F.

Kevin