It seems to me that in 1960, Mopar changed the Plymouth windshield shape..hence a 60 windshield wouldn't fit a 57-9..I defer to John Fowlie, owner of many cars, especially 57-9 Plymouths, and at least one '60..
assuming my previous response was correct, Vic, in addition to any 57-9 Plymouth convertible, you CAN still look for a 57-9 Dodge convertible, or a 57-9 Desoto Firesweep conv, or a 57-9 Chrysler Windsor convertible for donations..of course they are ALL as scarce as hens teeth..
Hi Vic, I have to agree with Roger that the '60 header will be different. I am in the same predicament with a badly rusted header bow, I'll probably have to fabricate one. ---John