I have every length Gates Belts part numbers that could fit 61 to 64 Chevy's for factory air, generator, alternator and power steering. 327 and 409 Chevy's.
Gates belts come in 1/2 inch lengths and .410 width. I have also used Goodyear belts similar to the number you listed.
I test fit them on my 327's and my 409's -- using Gates belts (through ORelliys ) and return the one's that don't fit. I even bought all the original style belts from Show Cars and tested them and returned them when they did not fit.
I found that part numbers (listed in books at part dealers) don't work good most of time, to get the proper tight belt and clear power steering pumps, steering boxes etc. Some of it has to do with having different pulleys and mounting brackets that change the belt length needed.
- I first tested the length with a string/rope like Kaycee said or start with the length of a belt that does not fit and then buy the ones shorter or longer as needed to get the belt to tighten correctly without problems.
- I use my list of Gates part numbers and some Goodyear part numbers with lengths to buy 2-3 belts that are close to what I need.
- As noted above I pick the belt that fits best and return the other belts
- I have some brand new belts leftover that I could not find my receipt(Gates # 7580 = 58 5/8 inch)
- This belt buying system also works great if you have a non factory mount for alternators (like a Allen Grove mount) on my 409's
If I recall correctly I needed A/C belts close to 59 inches to work on my A/C cars,
I can look up the part numbers I have for lengths 58" to 61".
Paul