72 Blazer got the shakes bad - HELP

[Scrat]

Hi All.
So I have a '72 Blazer that has an annoying shake/shimmy at 65mph. (It feels like a tire is out of balance) It starts to shake around 55-60 and is worst at 65 and then is better at about 70. I know, no biggie, drive 75 but my problem is the road I travel on mostly has a 65mph speed limit. I've been dealing with this for years now and dont drive the blazer as much as I'd like because of it. I cannot replicate the problem in the shop, only on the road.

What have I tried so far...
Balancing the tires, new tires, checking the axles/wheels for runout.
New shocks all the way around including steering stabilizer
rebuilt rear end - new bearings and axles
repack/check hubs etc on front end and new ball joints
new u joints/ balance drive shafts
New/rebuilt drive train including engine/tranny/transfer case
installed power steering

All this and I still have the shakes. Anybody else have anything like this happen? What did you do? Is there anything I have left out/overlooked?

I'm thinking my next step is to do body bushings and suspension (lift 3"). Perhaps the springs are shot ? I dunno.

Thanks for any help or guidance.

(pics to follow )