I have a 5 speed with the engine mods you want to get. My stock clutch didn't hold up very well and I didn't abuse it. The modifications didn't fry the clutch inasmuch as they accelerated the demise. Many thousands of miles before I BOMB'ed the truck, I took a long trip pulling a 31 ft Nomad TT. After that trip, the clutch started to chatter. Being that I probably needed a learning curve on driving a diesel powered truck(this was my first, low end torque, etc. ) and the possibility that I got a sub-par clutch from the factory, probably did my clutch in. If you drive well, your 6 speed may be just fine with the stock clutch. I would save up for a clutch just to be safe, though. Good luck. The combination you are going with is a really sweet towing combo, also.