Will this bore clean up, magnum head content too.

Dingle ball hone it until its cleaned up and then measure it. Hopefully itll be ~.032 over and clean enough to not catch a finger nail. Dont worry about the crap over the ring lands. Ball hones wont take much but itll help your to take the edge off anything left. Imagine what a 30 year old barn find cylinder looks like and guys start them up all the time with fresh gas and topping the oil off.