[FirstOwner69]

I just did this a month ago. As I recall they are 5/16" course thread just like many others on the truck. Inner fenders are a good example. My 69 were hex head with captured washers, but others (perhaps a year difference) were pan head phillips. I took some pictures last year in Phoenix of 2 beds that were taken off trucks when they were new. One was a 68 the other a 71 or 72. One had phillips and the other had hex. I think it was the 71/72 that had phillips.