Perhaps you could combine the cans and endbells from 2 budget modified motors that allow for adjustable timing. Then use 27T armatures, and adjust the timing equal and opposite. Unless you can find a reverse rotation rebuildable stocker. I think I saw these back in the day, not rebuildable thou, but haven't noticed any lately.

I used a single motor variation of this to get my son started. A stock arm in a mod can with very little timing, and really low gearing. Reduced speed, increased motor and battery life. Even with tired old 1400s it would go for nearly 30 minutes with very little brush/comm wear.