What is the difference between a 1973 440 car engine and a 440 industrial out of a motorhome?

The 440 in a car has the same "short block" as does the RV or industrial motor. That means the block, crank, pistons, rods are essentially the same. In some of the RV motors the crank may be forged rather than cast, and the rods the "Six Pack" High Performance (HP) rods. The cylinder heads is where the differences come in. Some RV's will have the "car" heads, and some will have a different "RV" head. The biggest difference in heads is extra water cooling passages near the spark plug in the "RV" type heads, and a "figure 8" shaped cooling passage entering the top of the block in some motors. Additional differences are extra strengthening ribs on some blocks near the freeze plugs, and additional iron near the crankshaft bearings in some blocks. However, for all practical purposes, the "RV" motor and the "car" motor are the same in the blocks and heads.

The biggest difference between "RV" and "car" motors is in the camshaft and intake area. The camshaft in most "RV" type motors is designed to increase the low speed torque at the expense of high speed power. Likewise, the intake in the "RV" motor is often a two barrel carburetor rather than a four barrel.

Finally, the brackets, accessory mounts, and other external equipment on the engine are usually very different on the "RV" motor than on the "car" motor.