Addco still lists them in their catalogue, but only the two biggest ones they offered. Addco IIRC uses a CNC bender to mfg. theirs so they should be able to make you one any size you want, cost...? Mucho I'm sure.
http://www.addco.net/aftermarket/catalog/chevrolet/https://www.summitracing.com/int/parts/ ... odel/monzaSummit shows only the rear available with Addco #672 which sounds like the right one to me but they don't have a front one listed anymore. Beware when I bought mine 5+ years ago these were expensive (everything is more in Canada though)
Like I've bought whole cars for less than half the $$$. I have about 3 rears (stock) of different sizes there is only small dia. changes, hard to do by eye. Harry
I'm not a hoarder I'm a preservationist 78 Monza Spyder (~Soon(ish +/- I guess) To Be 2+2 with Spoilers)