Hey CP what about the Magnumforce A arms they have a set of dual adjustable for $400? What do you think
You still have adjustment with those on the front and rear A-arm cams. So the double adjustment isn't really a feature you will use.
Realize there are other suspension improvements that will have a much bigger impact than just stronger A-arm with poly mounts. You can get good handling caster alignment numbers from a $30 pair of Moog 7103 Offset Upper control arm bushings.
.99 or bigger torsion bars
front and rear sway bar
good shocks (Hotchkis bilsteins or QA1's)
good rear leaf springs
frame connectors
then upper control arms and adjustable strut rods. I'd go with the Hotchkis A-arms especially on a E or B body because the bump steer reduction geometry. You get two improvements with one part. I think you will feel as much or more handling improvement from better geometry as the stronger A-arms. Especially on a car built to the Street Cruiser end of things.