Trying to get rid of some things

To return to your original question, most of the vacuum stuff is for EGR and gas fume recovery (charcoal canister). The big round box on the intake manifold is a "vacuum amplifier", as I understand. Indeed, my 85 M-B has a similar but smaller device. I think if you disconnect the tube to the EGR valve, it will stay closed. A guy on ebay sells a block-off plate for ~$15, however you may want to change the intake anyway, to a 2bbl or 4 bbl. I don't think the charcoal stuff hurts, as long as it is all working. It might even slightly improve your mileage by recovering gas. If you change to an EFI setup (few have done on a slant), it would serve no purpose since no carb bowl to evaporate.