The 60's/70's RG block 225 motor would be perfect for your 1 ton truck. That motor is well know for its realibility and durability since it has a forged steel crank(up thru 76)and rods. Main bearings are the same size as the Chrysler Hemi V8. The truck motors also had shot peened forged steel cranks and roller timing sets. From 72 on the valves were induction hardened for unleaded fuel. They all had solid lifters until 1980. Stay away from the 80 and up smog motors. The 225 motor has a nice rod ratio that made for great low end torque. Used in many commercial and farm application as well as marine use. Many of these engines were/are still in aircraft tugs, school buses, combines etc. A good 225 will outlive your truck! Some people even run turbos or nitrous on them with the cast pistons. (not recommended)
Besides, used 225 oil dipsticks are cheap these days..
