Seems many here have that idea of a dream car - Turbo 617 + 5speed in a W115. I only have heard of two....one was in Canada and another was featured on this forum & it looked pretty rough...never heard if it was ever finished.
Your 240D is the same colour as the '69 220D my uncle used to have, that got me first interested in these cars. Though you need to repaint your hub caps...they look like they are from another car (or just strip them & leave them chrome....that looks good too).
Are you sure your glow plugs are dead? If you've never had one of these before, you might not be finding the exact right position for pre-heat. If it starts in under 10 seconds when cold, they're heating up while you crank.
You will love changing the oil! I'm due to change mine this week....can't wait to get....um....oily. Oh then there's the oily air filter too, they don't call it "oil bath" for nothing
