AP -- who was known for his bruising style as a running back -- displayed a great physique ... weighing in at 218 pounds according to the scale.
Bell -- who was more known for his shiftiness coming out of the backfield -- hit the scale and appeared to be in awesome shape for a guy who ran for over 6,500 yards in his career.
LB weighed in at 204 pounds on the scale ... so he's conceding a 14-pound weight difference to Peterson when the two collide on Saturday.
But, the video of both future Hall of Fame running backs sparring this week has boxing fans encouraged that both men will deliver a good, solid fight.