Hi,
I just did a R&R on mine and ended up re working the threads so I could re-use them. I thought about using ss hose clamps but managed to salvage the u-bolts. I am very confident that the hose clamps would work fine. I would also suggest putting a rubber pad between the mount and the exchanger. I use a 4" furnco cut in half.
Good luck!
I have several pieces of heavy equipment and 4-inch exhaust is the norm. Check with NAPA or other heavy equipment manufactures, peterbuilt, cat, kenworth, etc