today i bought a 99 montana 3.4 for 1300 cash title in hand,it has 201xxx miles and the previous owner was to believed to bought it new in 99 and the trans isnt slipping and it runs overall good,i did i get screwed or what and if i dont dog it out how long can it last and whats the most the gm 3.1s and 3.4s could run on original motor?