[Walt Fricke]

If my engines were as clean as that I'd think I'd died and gone to heaven.

Checking for broken head studs, for sure. If you find one or more, now you are in for more engine work. I was actually able to replace a broken stud with the engine in the car, but only because of which one it was - with some grinding on some surrounding aluminum I could get a vice grip on the stub, but it might have been the only one in the whole engine where that could be done after the air deflector was removed (a chore in itself on an assembled engine).

As for the 915, the three shift synchronizing parts are the slider, which mates with the "dog" teeth pressed into the actual gear. Both of those pretty much wear together, and if one is buggered, the other is also. As the synchro ring (the other main part here) wears it looses its ability to synchronize, which leads to wear on the teeth, so that is the third part.

But why not try draining and looking at how much fuzz there is on the magnetic plug, and seeing if new Swepco makes a difference. I'd not put a lot of money on that, but if it works it sure beats the alternative.