Sorry I'm a bit late on joining this discussion. Seems problem has probably been identified. Would probably have suggested rear drum brakes as I had a major problem caused by rear drum brake disintigrating and one pad jamming under the other. Had some clunking like yours but unlike yours my rear wheel locked solid. Oddly, also had a brake cylinder gone but mine was on the rear wheel. As to effectiveness of handbrake, mine is fairly good and will hold the truck on a hill without a problem. Don't know if I could do a handbrake turn though as I haven't tried it. Happy birthday Paul. Hope the truck is sorted.
