Finally!
Mixed up some ATF/Acetone and kept squirting in there over the course of 2 days.
Also, finally got the mufflers off. That really helped, as I believe they were indeed causing binding (as I couldn't be on both ends of the bike at the same time)
Once the mufflers were off, I lightly tapped the headers BACK into the heads with one of those rubber mallets filled with BBs. Once the right side moved, I knew it was free.
Light alternate tapping on the header ends where the mufflers go on, right then left then right etc, eventually freed the headers from the exhaust port.
The crossovers would not budge tho, and now I realize 2 of the welded crossover clamp bolts were missing (1 ea from front and rear), and I managed to knock off a 3rd from the rear when my 2x4 block slipped and clipped it back when I first began and was wailing on it a bit.

So, while all this allowed me to get the heads off - nice and clean looking BTW - the header/Xover combo is still all one piece, and I can't get it to clear the centerstand. I've got the Xovers soaking in ATF mix, hoping they'll let loose so I can remove the pipes, as it looks like I need to replace the Xovers anyways due to the missing clamp bolts.
Meanwhile, Bombars has the heads and can start work on 'em anyways.
Another question - how best to clean the pistons?
Thanks for everyones help on this!