Let's clarify things a little- - - -is the engine in running shape now, or has it been sitting for 40 years without being started? There's a BIG difference in a runner that hasn't been on the road recently, and one that's sat without starting for that long. If it's currently in running shape, be sure it's getting clean fuel (old gas tanks are bad about ruining otherwise good engines with varnish), change the oil, and drive it like you're breaking in a fresh rebuild. No prolonged periods of full throttle, no lugging, where the vehicle doesn't accelerate smoothly when you step on the gas, and a varied mix of slow speed and highway driving.
Jerry
