Make sure you buy brand new balls, even if your old ones look "decent"
because they are probably pitted and that is like rolling balls of sandpaper over your newly refurbished playfield.
Fix the problem with the score reel resetting problem by fixing the problem,
I do not recommend swapping reels.
That would be like replacing a dripping faucet with a new fixture, when just a simple washer replacement (switch blade adjustment) would do the job.
I also noticed another comment about the pop bumper caps
with numbers wearing off;
this era Bally EM pin often had bumper caps without any markings
or numbers imprinted on them.
If you want to keep it original, buy new caps (if the old ones have bulb burn marks)
but without any labeling, see flyer for reference at ipdb.org .
Also suggest you visit www.pinrepair,com if you have not done so already.