That is one helluva vintage lineup you got there. That Big Bear is just awesomeness!
That Sand Scorcher is one of Tamiya's classics man. It is one I wanted as a kid.
The problem I am seeing with all the aftermarket shocks is the springs are too stiff. What I would suggest is add weight til you have at least 50% droop, and even more in the front. But then you raise your CG. So that means the lightest spring you can get to keep the shocks drooped will give you...
I run close to full droop on mine. The Carnage handles stuff pretty good, but I haven't really had the chance to reslly push it. It maybe has 1/8" of travel left on the shocks sitting dead flat.