I received the belts I ordered, installed them, and took pictures. The picture shows a stretched 50.5 inch belt on the alternator, which I swapped for a new 50 inch belt after the pictures were taken. However, both of the belts are too thin (The AC belt is squeaking just a little because the inner part of the belt actually touches the inside of the pulley groove). They're 10mm wide, and they should be 13mm wide, so I have new belts on order (http://www.autozone.com/cooling-heating-and-climate-control/belt/duralast-v-belt-belt/112714_0_0/ and http://www.autozone.com/cooling-heating-and-climate-control/belt/duralast-v-belt-belt/305128_0_0/). The new longer belt is 65.5 inches instead of 66 inches, but I think that will work better. The 65 inch belt I ordered is too small, and the 66 inch belt is long enough that I can max out the tensioner. The alternator belt is a 50 inch belt, but there is a lot of wiggle room with the length of that belt. I'm also running a CS130 alternator (off of a 1987 Corvette with a pulley swap) which may (or may not) make a difference. I'm also (as far as I know) running a pulley setup from a 1970 engine. I know there are different pulley sizes for these cars/engines, so again, your experience may vary. But, this should at least get you in the ballpark of what size belts to use. I also ended up putting the AC belt farther away form the engine while experimenting with the belts. Not that it makes much difference, but part of me worries about the extra leverage the alternator belt has on the bearings when the alternator belt is on the second groove. (I was getting a noise, so I swapped the belts around, but it turned out the noise was just because the belts are to thin and I left the belts installed the other way.) As promised, here are some pictures.