I used to tow a 6,000# boat fine with a 4.2l V6 with a stock clutch. I do use kudos for staying in 4th gear.
However, before assuming your clutch was/is burning up, did you ever check the Ebrake?!
I had my ebrake seize up on my '99 twice, and both times people told me my clutch was burning up, and it really was the drums getting scorching hot burning up brake pads.
Also, how were you driving up the bridges? Slow? Fast? Were you shifting a lot?
I can't imagine burning up a clutch hauling something if you knew how to drive stick well, even if it was way over the payload.
Finally, to give you a hint, to help you out pulling your boat out of the water, I highly recommend setting the ebrake lightly, enough to put resistance on rolling back. It will save your clutch big time. I learned that trick a by a fellow boater.
Oh, and if you want a HD clutch, try getting a Centerforce Dual Friction clutch:
DF983982 for $558.64..