Glad that the pedal was removed without damage to the crank! Have you checked to be sure that a “proper” pedal is able to be threaded onto the crank arm? Always hard to say what “Bubba” did to get the cheapo MTN bike pedals mounted. I suppose it’s possible that some level of thread locker was used.
Congrats on the Miyata score! Nice bikes. I have two, an ‘84 Seven Ten and an ‘85 Two Ten. Trying to keep them mostly “period equipped”.