well as a training teacher in my Advance Sweeper Training class told me one time, "these machines eat dirt, thats what they are made to do" so 16hrs of 'eating dirt' is certainly enough time to start the chain reaction of wear inside the engine to cause that wear.

It's amazing how much wear dirt can do to an engine in a short period of time. I had come across a diesel engine at a customers facility wear out in a short time because of a air leak on the back side of the air cleaner that the servicing tech never caught. I just happened to get called out on it for a hard start issue and while i was diagnosing it i heard a rattle and found the rear horn on the air cleaner was broken off from the housing. We suspect it ran that way for 2 service intervals of 200hrs each so thats approximately 400 hrs of run time that it was eating dirt. Needless to say they were not pleased about that, we had to eat an engine over that incident.

i'm with bb on that.004 not being excessive warpage on the head surfacing, thats not that much to cause a head gasket failure issue like you have been having, unless the head was never re torqued after initial break in. Of course after the last gasket replacement if the same head bolts were reused that may have played a factor in the failures, once those bolts are stretched that may cause issues later on. Usually the main problem with bolts once they are initially torqued down is they never really retain their ability to hold the torque value and they keep stretching out so the head may have loosened up over time allowing for the failure(s).

It was mentioned about possibly using automotive pistons and rods? ehhhh... this is an industrial engine, theres not much on the inside that is 'equivilant' to automotive grade materials. Most of the components are made differently, heavier castings, their differences may be unnoticeable by the average mechanic but someone that has experience with engines would notice them, such as thicker skirts on the pistons and even the rods may be slightly different. So i would be weary of trying to supplement alternate parts other than industrial grade ones. ;o)