I kind of just feel for BDC. When you get your new truck roll the flywheel over with the glow plug out, you will feel it gets very difficult at TDC and before TDC. Roll the flywheel back and forth from where it gets tight on both sides then just pick a spot somewhere in between. Or take the glow plug out and look in there to set it at BDC, do this by hand so you don't end up with fuel in your eye.