I do NOT want to add fear to the recipe of repairs. But a simple thing like no heat can also be a head gasket issue. I would get a pressure tester and check the cooling system. Sometimes it will hold pressure and still be the head gasket. I had an M1009 that would hold pressure for days. But one of the symptoms was no heat. And then it would get heat at highway speed and stay nice and toasty. But in city/town driving lower RPM's No heat. Also the coolant recovery reservoir would be full of coolant every day. I would unbolt it and pour it back in the radiator. Not to scare you but keep that idea in the back of your head. I have been removing the heads on any CUCV's I have apart for rebuild. So far 3 have needed head gaskets and they were good running vehicles. Just that 30 years and acidic anti freeze is taking it's toll on the thin steel head gaskets. Head gaskets are much better now then they were 30+ years ago. Doing the heads is not a real big deal as long as you don't have a set of cracked heads. Gaskets, bolts, and get the heads checked out at a good quality machine shop. No need to add studs and get out of budget. It is a very reliable engine and it is old school. Simple. Remember to keep this acronym in mind every time you work on your CUCV. KISS "Keep it simple, stupid" because of the simplicity it will just keep going in stock form the way it was designed to do. Think about it. Everything you change and convert thinking you are making it better and more reliable has already lasted over 30 years. So as a rule. If you can't unbolt is or unplug any modification you are thinking of doing. Don't do it. OK enough of my gloating. I just found over the years to keep looking until I found the problem. NOT change everything that leads me towards it and create more issues and spend fool's money on the issue when it is already there and I am trying to avoid it. Bad head gaskets don't go away. But please do check for them and pay heed to the results of the diagnosis. Have a Great Day. it is pouring down rain in Pennsylvania today. Time to rest.