Well the STRONG GTS which is a steel frame, and a downtube for l.a. batteries which was sold as an electric bicycle and had a 250W'ish brushed geared motor on the rear has a wide rear dropout, I can't remember what I measured, but its atleast 160mm and what happened was with my motor I always had to be squeezing the rear inward, no big deal. Whatever the nominal rear dropout are 135mm for the flats of a rear motor. Yes you can search here on E.S. that name and you will find it. I bought mine used, with a non working battery and subsequently burnt the brushes out on a climb fairly quickly with my lithium ion battery.
However to ramble on, my plans for the bike that I just took out of storage yesterday was to buy the MXUS 5000W rear motor from the factory in China, lace it into a 16" motorcycle rim with a Shinko 241 tire. That motor needs 160mm I do believe. Then the welds on the bike are well what any BSO department store sells so the welds crack and have to plate up the joints. I rode it for 6m-1yr before the shock mount broke, while on a ride quite a ways away from home, and had to call for a ride. I bought a shock meant for a gasoline scooter from Toys 4 Boys here in Calgary, AB Canada who sells e-bikes, gas stuff, lights whatever they can fill a container from China with. I am over 300lbs so no regular bicycle shock will work. I did the floor test on the shock, it doesnt budge on the lightest shock lock setting. Plan is to either heat the spring, or shave off material if I require a softer ride. Or just look for a suitable replacement spring that will fit.
Here is a link to an E.S. discussion on the bike mentioned. Find them used somewhere, garage sale, community bicycle stores that help customers maintain their bicycles and sell used bicycles. Which is where I bought mine from for the simple fact about the battery location.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=88047&p=1316453&hilit=strong#p1285014