What are the differences in these motors? I've heard of a diesel longer stroke crank. I've got 200,000 miles on my M42. I pulled the pan and found NOTHING - still, it's not going to run forever. If you have to swap out motors but still want to keep the M42, what are your options for increased displacement and the cost of each? Being fairly new to BMW's, I 'm not really up on the models and what came and goes with what. Just looking down the road a bit.