Long story short, my brother's 2001 YZ426 threw a rod or something and basically exploded parts out the bottom of the engine. Tore it down, and the head is still in great shap, but that's about it. Cylinder skirt is cracked, piston is trash, crank and rod are broken, and you can almost put your fist through the hole in the cases. The transmission seems alright, but whoop-de-doo. Anyway, I'm trying to piece together a motor for him. I found a bottom end off of a 2000 YZ426. Will this fit in his frame? If so, will his 2001 head fit on it? The Ebay bottom end needs a crank. Will a WR400 or 426 crank work? Which years will plug and play? How about pistons and cylinders? Thanks for any advice I can get here. I know the 450's from 2006-up real well, but the 426's not so much.