Hi, I waited in case anyone else chimed in.
I believe the OEM bars were only available in 4 sizes, .92,.94,.96,.98.
Yours are probably the .94s if original.
Now I would guess that a Road Runner equipped with 318 would have the .96 bars, as would a Satellite equipped with HD suspension, or 400 4v.
Original 440 cars, and police, would use the .98 bars.
These numbers refer to the diameter of the round portion of the bars, so measure yours! Who knows what's in there after all these years, and check both sides,just in case
You'll note that these sizes are larger than the 62-72 b and e bodies.
That's 'cause they're longer and have to be fatter to have the same spring rate.
With the emphasis on handling these days, finding skinnier bars may be tough.
I think sway-a-way lists fatter bars, maybe they could custom build you a skinnier set.
I always wondered if a machine shop could turn them a little smaller?
Of course they'd have to be very straight to start with.
Don't forget that the R bodies used the same size bars, and these would be the newest cars -'81 that you could look for. Newport, St. Regis, etc.
I got a set of the big bars off a St. Regis police car years ago.
And then I got some bigger ones from the New Jersey suspension co.
Let us know what you find.