I have a 700R4 in my 1991 GMC 4x4 Z71 with a 430hp 383. I have broken several transmissions in the past. The last one that I had built for my truck has lasted a long time. Tell your builder to not be too aggressive with the shift kit. If he makes it shift so hard that it barks the tires under full throttle you will break internals. A nice firm shift will make it last a long time. Also, spend a couple of bucks on a good converter, you will eat up a stocker if you pull a lot of weight with a higher hp motor. Make sure that you have a good trans cooler, if you are using the one that came on your truck with your 4L80 make sure that you flush it out. You can make a 700R4 hold up to a lot of hp in a car but the weight of our trucks seem to kill hard parts. If you are serious about building a 700R4 that will put up with some abuse PM me and I will give you a list of all the mods that I have done to my transmission. My truck weighs 4800lbs with me in it and I have gone 13.92 @ 98mph with this combo. Make no mistake a 700R4 will never last as long as a 4L80E nor will it put up with full throttle trailer pulling.