I put a Bafang BBSHD motor and a dolphin type 17 ah battery on a 30 year old Trek 930 we had. Probably 300 to completely renovate the trek. Bought the lot from California-ebike.com. I recommend them.
I don’t intend to go fast. I wanted overkill for reliability. Only 100 miles so far, first couple trips pf adjusting etc, now it’s just great.