Ive posted before my most trouble free crank has been a simple eagle forged 4 inch crank, its in my sprayed street racer that runs 6.0s at the track.

The K1-s I had trouble with, one had a main way off and two others had mains so far each way I had to go .010 on them, however with K1 being a good product I got both of the worst K1-s from the same place, same time, that I didnt know was closing shop soon after my purchase and both cranks were dated, so maybe I got there off the shelf not so great ones or maybe even returns.

Just like anything, good machine work and proper assembly goes way further then the brand on most of our junk.