It sounds like you're on the right track. I know Reese used to make a universal receiver for Chevy pick-ups that fit from the 60's to the 80's and it was designed so you could adjust the width. If the numbers you looked up fit the width of your frame, pick one. You will probably have to drill the holes anyway. Newer trucks come from the factory with the mounting holes already in the frame. Lie the guy said, measure twice, drill once. Oh, and check the torque on the bolts after you have driven the truck some and DO NOT WELD the hitch to the frame.