So far so good on filling the bushings. I was WOT in first and second many times this morning with no thumping, vibration, etc. Just smooth acceleration.
I agree with Seeeee Yaa, even if bushings come to market, they will be a bear to install. Not an easy job for a weekend do it yourselfer, like myself.
For those interested in trying out the poly filler method, if replacement bushings do come out, the filled bushings will not be any harder to remove than stock ones. Also, the rear diff can also be removed just the same as stock. Other than costing a few bucks and being a PITA to clean up, I see no drawbacks so far to using the windshield poly to eliminate the growling rear end issues.
After looking at the rear Lower control arm bushings I decided to leave those for another day.