Bill posted this on the V8 board:
http://www.v8buick.com/showthread.php?t=69059&highlight=65+gs+Radiator+hoseThere is a pic there too.
>>>>went through this a last year on a 65 GS, best fit I found was to use about12 inches, starting from the engine side,of a 70/72 Skylark upper hose. I have a NOS lower for a guide and bends are about the same and it fit great. The part number for the 70/70 upper Skylark was XL 107 from Auto Zone, and I think it was made by Kelly Springfield or Goodyear. It cost me $6.99 at the time and I bought two just to have a spare. Thanks Bill Sangster<<<<<
More posts from V8:
>>>>I went to NAPA today.... cross referenced them to the gates numbers and showed me the hoses.
still need some triming........ NAPA #8817 upper and NAPA#8484 lower. They are both an 1"and 1/2 ID.
Bill Bailey<<<<
>>>Here are some cross reference #'s someone provided me but have yet to cofirm them being correct.
Upper hose inlet- Gates 20542==alternate 20704
Lower hose outlet- Gates 20466---NAPA 7272
Doug<<<<
Double check the hoses listed above to make sure they will fit.
What hoses are you using for the top? I'll add the info to my database :D
