Just my opinion, and I could be wrong. But that JB Weld is never going to hold. Just not made for that. You can still helicoil the bolt hole, might need to use an oversized stud, tho, and drill out the manifold hole to hold it. From the JB Weld website,
How much heat can J-B Weld withstand?
Original J-B Weld can withstand a constant temperature of 500º F. The maximum temperature threshold is approximately 600º F for a short term (10 minutes). Refer to individual product packages for more temperature information.

I'd probably invest in some head gaskets and pull the head out and have a machine shop install a new stud.



I just pulled a dead (lower end) 5.2 out of my 98. I haven't had the heads off, but compared to your rusty things, mine are very nice on the outside. You could have one or both of them reconditioned and be way ahead. Best part is that they are yours for the cost of shipping (which would be quite expensive.) You don't say where you are, but it would be worth a drive if you're anywhere near the Tucson area.

LMK, if you want them or only one. I'm going to take the old engine to the scrapyard as soon as the 98 is ready to move.

 

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Surface rust isn't a big issue as it in no way affects performance and can easily be cleaned. I also wouldn't expect an engine that sat in a yard to be completely rust free. As I said the insides are extremely clean and in great shape. Only problem with the machine shop idea is that the shops around here charge very steep illogical prices, and money is a concern, so buying new heads or gaskets is a large wallet hit. My dad has alot of experience building engines, he is just a lazy **** with repairs sometimes as he is certainly a master at half assing things when he gets frustrated (like you would be if an ez out snapped off inside your head). I've expressed my concerns just wanted to run it by you all. Not interested in the trash talk like comments or offers. It's not my dads first rodeo on engines, and at least his third magnum rebuild. Just had concerns about his lazy and probably slightly intoxicated repair. THANK YOU to those with legit helpful comments.. Also wanted to say that when we got the engine, it ran in car, and ran very good, and was certified to run when installed AS IT SAT at the time.. Not just a cheap crap engine.

 

The reason this repair was done in the first place is because a local professional engine rebuilder said he has been doing this type of thing for years and it holds up. Just wanted to note that

 

Well, you've already made up your mind.

Either the JB Weld will hold or it will fail, you'll just have to find out.

 

Well it's not really up to me, but yeah either it will work or it won't and ill let you guys know. Wouldn't be coming out of my wallet to fix it again. I was mostly just concerned with side effects of it failing which was my main concern. I'm certainly willing to find out if it does hold as its a cheap fix, so if it works its a money saver. I was just worried about driving it and then something major breaking. I'll probably make sure it is fine though by letting it idle and rev some too, while its parked in driveway once the engine is in.