Removing all emissions control/vacuum systems: Good or bad idea?

They can't expect people to maintain those vacuum emissions controls today, especially since parts aren't available, so good they don't require it. If you do want to keep some, I have most parts from a spare 74 slant engine (for my 64 someday), you are welcome to if you stop by on your next trip to Tahoe (PM). I recall testing the hot air diverter on the air cleaner and found it still actuates the flapper door and holds vacuum, plus the exhaust shroud and duct. That is a nice thing to keep to heat up the inlet air on cold mornings. If you ever get your engine to MPFI and electronic spark control (like I plan), that will get your emissions much lower than the 1974 design. There have been posts describing the complicated distributor vacuum advance controls in those years.

I wouldn't worry about EGR, since neither my 96 Voyager 2.4L or 2002 T&C 3.8L have EGR. The same engines used in cars did have EGR. The EPA classifies minivans as "trucks" so lesser emission and safety requirements. Makes no sense, so don't feel guilty getting better mileage and polluting less in a car than your neighbor in an F350 with an always-empty bed.