if the truck was well taken care of and kept in good shape milage shouldn't be an issue. those miles are highway miles, a lightning isn't made for offroading. so why in the world are you worried about 100k? if you really think spending another 4k on your friends truck just because it has 40k less miles is a good idea go ahead. but i sure as heck don't. are you considerin gthat you will save 4k if you buy another lightning with 100k miles you will have$4k to spend on making that sucker fast. and in generally moding it you will be replacing that which might cause you problems. heck you could easily rebuild the engine so its faster than it was with $4k, so your still wanting your friends overpriced truck?