run 'em up till they strip or break, then back 'em off 1/2 turn....... [i can't resist !]
living in the rust belt, and owing a junkyard when these cars were fairly new, it was common for the bolts to break off or the weld on the nut to break loose when trying to remove the K for a customer.
it was much less work to cut the mounts off the K, bolt them to the intended engine, then lower the engine onto the original K and tack them. [with a stick welder of course. ]
pull the engine and fully weld them up. you could also find out if the K needed modified in any way, and do it at the same time.
a hack ? of course it was, but back then, we didn't know any better, or even care.
wouldn't even consider such a thing today.