I did a generator to alternator conversion on a 1953 Morgan. The stock belt was too short and no longer fit and there were no other 20mm belts that fit. V-belt Guys had some 19mm belts that would appear to work. Also, because the 19mm belt rode farther down on the pulley I couldn't get an accurate measurement for length and had to guess. Because of favorable pricing, I ordered multiple belts in 1" increments until I found the correct belt. I need to order a spare belt for the future now. Good service, great prices and they have what I needed. These guys are great. I am posting them to my online forums.