Open the door. there is axle ratings in the jam. Ratio is on a tag on the diff cover held on with one of the bolts IF its still present. It could have 4.10-4.88. Is it an auto or stick? Look at the block above the starter, the engine sir is cast in the block. Should pull almost and car trailer just fine. I used a regular 3/4Ton to pull my open car trailer with 318/4spd 4.10 grs. That style brake controller is the older style setups.