Usually the rear bar is smaller. (talking soild bars here) I've used Lincoln MK 4 rear bars on many vehicles If I remember correctly theyre 5/8" or 11/16" diameter. Both my '54 Chevy Wagon and '73 F100 have MK4 bars in the rear and 1980's BIG Ford station wagon 1 1/8" bars in front both handle surprisingly well. The F100 is lowered 4" and the Wagon is raised 11".

This is the F110 before it was painted : My wagon is the one on the right, the Ford wagon is Jesse James's, you might remember it from Monster Garage.

Studebaker used 5/8", front and rear on some early 50s cars, but most did not even have a rear bar. Later, they went to 3/4" up front, but did not mount it properly till 63, when they changed the frame mount design. For decades, Dave T-bow has offered a 3/4" rear bar, shaped exactly like the original 5/8" bar. I have installed several of them over the years, on 56Js and GT Hawks. Around 1990, I also installed a rear bar from a late 60s/early 70s MOPAR of some kind, but I have forgot which car, a Barracuda or something similar. I had to narrow it by a few inches to fit it into the 62GT, but it worked out nicely, and is still on the car. I am sure there are several other possibilities, but most require some kinda alteration, whereas Dave T-bow's bar is no muss / no fuss. I believe his price is still reasonable too.

A rear bar on a Stude reduces lean in sweepers, i.e. on/off ramps, and zooming through mountain twisties. But it's not real noticeable, with or without, unless you are towing, then a rear bar is critical. In our current three Hawks: the 56J has a Dave T-bow bar, the 62GT has the MOPAR bar, and the wife's 63GT has none.

Well...yeah, a "matched" front AND rear anti-sway bar "pair" is...very...noticeable ! Much more than just a front ! The addition of "both" bars goes a long way in keeping the fish in the fish bowl !!! If you are old enough to recall that commercial !

Jeff, since you don't seem to mind a little mixing and matching, the GM (Buick, Chevy, Oldsmobile, Pontiac) front bars off of most of their cars (Camaro, Monti Carlo, Firebird, etc., etc.) will work with a little bracket making.
There's nothing like flattening out a Studebakers cornering than adding a 1-1/8" GM anti-sway bar, and a factory copy to the rear of a Stude.

The main attachment (front) bracket needs to drop the bar down about 5" or so inches from the bottom of the frame. This is a bolt on proposition to the frame. Then many of us just make small tabs to weld to the front of the lower control arm for the connector links.
Note that the "arms" of the bar should be parallel to the chassis / ground, to work the best.

Then buy the 5/8" (I think) rear anti-sway bar that's sold by some of the Studebaker vendors, and bolt on in the OEM locations already on the car.. Whom ever took over the Fairborn parts may have them.

NOTE - Only adding a large front anti-sway bar will cause the car to not be in proper balance for safe (hard) cornering. You can add a small (5/8" or less) front without messing with the balance too much. But a larger front, and no rear can cause erratic handling situations. All of this information can be found in many different, "suspension" books.

There was, at one time, a drawing being passed around of a front bracket on this site. A "search" MAY find it for you.
If you can't find it, send me your address and I mail you a drawing of the bracket that I made up for my cars, of just some flat strap material.

It's well worth the effort ("both" bars !).

Mike