I have a 1976 motor home on an E250 chassis (actually designated E270) with a 300ci inline six and automatic tranny. It's doing fine, but am worried about getting repairs in case of failure of "obsolete" drivetrain on the road. Any suggestions for newer replacement engine and tranny? I don't need or want a bunch of power - about 150hp (from, say a 350ci V8 engine?) would be acceptable, and a newer 4-speed tranny would be a blessing but 3 speed is acceptable. Would be great if could just lift intake engine and tranny out of something and could then just modify the driveshaft . 1976 era vehicles had carbs, not fuel injection.

Unless your investing for sentimental reasons then you would be better off replacing the motor home. The type of swap your talking about would cost more then the motor home is worth.

I would be inclined to take really good care of what you have an see what happens. I recently did just that with a 1983 school bus, donated to WMU of Texas, with 162,000 hard miles on it. It's now traveling all over Texas, Oklahoma, and Arkansas selling WorldCrafts to keep women out of prostituion, poverty and human trafficking. I went synthetic all around--engine (6 qts. of Pennzoil Platinum 10W-30), transmission (4.5 gallons of Amsoil Torque-Drive), differential (3 gallons of Mobil 1 85W-140), and grease (Mobil 1 Synthetic). I had to replace the electronic ignition system (cap, coil, rotor, ICM, terminal block and capacitor), plugs, wires, and install a rebuilt brake hydro-boost. eBay and AutoZone were my friends for parts on an old B6000 GMC school bus--very few other places carried parts for it. I went over the brakes, changing the fluid with Valvoline brake fluid (2 qts.). You get the picture--good preventive maintenance may get you many more miles from your vehicle.

I agree with other posters. That is a strong engine, been around a long time. Probably has a good torque range for what you have. Newer engines would be near impossible to swap without all the computer parts, gas tank, pump etc.