I understand. But, unless hes BUYING an autox car, its probably a waste of his breath to ask.
As to breaking diffs with stock power, much of it is in how its driven. If the car is abused, the diffs will break. If the car is driven reasonably, they will last a reasonable amount of time.
Back in the day I was busting trannies right and left. I had just about singlehandedly cleaned out Cophers in Tampa AND Clearwater, as well as Ace of their 5 speed boxes. At that time I had an 8V rocco with a later model hydraulic head, header, exhaust, and a filter. I also had a puck clutch and routinely did clutch dump burnouts and powershifted the car.
Trannies would last me a week or two.
Fast forward to a few years ago, I had a stock 2Y box in my car for years, no problems. That was with a 1.8L 16V a 2.0L 16V, then a bad attempt at a 16V turbo and finally a very successful 8V turbo setup. The car would boil the tires by ROLLING on the throttle in 2nd gear. Never had a tranny issue until finally when 5th ate itself from a lack of fluid on a trip to Tampa.
I honestly think that what makes a huge difference is the way the car is driven and the cars maintanence. I never have a problem with hydraulic mounts. Then again, when my stock mount was wore out I bought a new one instead of a junkyard mount. And I put in all the bolts, including the one that goes through the starter.
I also have outgrown the practice of revving the car up and popping the clutch on every corner. That is basically beating on it. A 200hp turbo car will do a much more spectacular burnout and be putting more overall power down with a rev and moderate application of the clutch than a 110hp car will by having the engine revved to 6K and the clutch dumped.
But the shockload on the driveline parts will be ALOT higher in the second scenario, resulting in more broken parts.
Im not saying a bolt kit is a bad idea, but most of the people I see saying its a must are just driving retarded. If most of these people would quite driving like they are 17, their trannies would last alot longer.