The clunk is normal. No action needed. You do not need to flush the trans as it would have been done at 100K miles and is not needed again until 200K miles.
I've taken a few 350's up to 170K miles. Very few powertrain issues other than a coil pack here and there resulting in a misfire. Probably also due for ball joints by that time as well, but I'll bet they have already been done at least once. Check for a zerk on the BJ's. If present, apply a few pumps of grease. If not, consider installing zerks so you can apply grease.
Thanks! Prior owner had ball joints, new cooper tires, steering stabilizer, spark plugs, and new Monroe shocks put on when he bought it last March. He put less than 1000 miles on it and decided he wanted a toyhauler instead. A lot has been done I'm just trying to see what else it'll need before next spring.
