Opinions? Ideers? VERY sick (old!) 220D

Gotta' customer's '72 (?) 220D/stick sedan here. Low (140K) miles, starts great, lotsa' power (for what it is....), no abnormal noises, but major (oil) smoke and oil consumption....and when it smokes, it misses like a gas engine with a plug wire pulled off. Start it cold, it runs great, turn up the idle knob and put it on a high idle, and within a minute or so, it's "missing" and my parking lot is literally fogged right in with oil smoke. The miserable thing doesn't even have an excess of crankcase pressure. All I told the customer is that the car isn't worth tearing down and fixing right.....but anyone got any ideas? I just want it outta my driveway, and I'm curious what ails it....but not curious to work for nothin'...

Thanks!

Jim Steere