What year is your cruiser? Does it have the seven fixed nuts across the top of the windshield to mount the channel. My 9/67 68 factory model hard top has them. Bought a 73 FST over twenty five years ago and installed the bows on the 68 and bought a new Kayline top while there were still available.
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Back in 2009 bought bows and used Kayline top off a 67. The channel was shaped like the early channel when they were welded on but used the same seven bolts. Late model FJ40s no longer had the fixed nuts but did have the holes where they would go. Assumably for markets that still got a FST. Like mentioned the OEM channel has a radius to match the windshield which makes it simple to tell where it mounted.