Hello Everyone! Just found your site! Great!
 

Hey!
I have been "tweaking" my Diplomat for the last 1 1/2 years, now I have a place where I can do some comparing and find more ideas.
This is a cool site.

Welcome to the site! What's your goal for the thing?

Shooting for 28 mpg
 

Which would be wonderful for a barn door shaped car!
We also own a 1998 Chrysler Concorde that gets 28-30, of course I would like to see that!

Are you averse to aero mods, :)?

Only 28? You can go higher with some carb mods. Someone on here was talking about making mods to the carburetor that will increase mileage but decrease driveability. Supposedly he hit 90 mpg in an old Dart, but said that it was pretty much undriveable.

Not Too Many
 

I (sorry) LOVE the bodystyle of the Diplomats, always have.
I am considering a "spoiler" for the front bumper, to split the air over that mammoth grille. Also considering underpanels for the chassis.

Those things sound like a good start.

If you're going to continue driving the barn, perhaps do an EFI/engine swap?

Have a Hydrogen Generator that while I was testing almost blew up in my face, but as repeated, is very high maintenance.
Still have factory Holly carburetor, haven't thought much about heavily modifying it. Have to drive this thing 50 miles interstate every day, don't want to get run over. The mileage I am getting is at 70 MPH!

Called Holly and Edelbrock about their Fuel injection conversions, gave them ALL vehicle specs, both told me I would only see 2-3 mpg improvement! For $1000, Told them to keep it. And, at least I can limp home with a carb!
Also have in a box in the garage a 360 ci engine, so engine load would decrease at 1750 rpm.

I'm sure you can whip something up yourself for a bit less money, eh?