Super stock spring weights

[Darter6]

I think stiffer with the stick is the right way to go.)

And the 4 speed

 

[66Satellite47]

I am also trying to figure out SS spring weight ratings. I have a '66 Coronet that I originally bought 3800# springs for, but have since changed to 3600# which seem to work better (automatic trans/footbrake). Now I am scrounging parts for a '63 Belvedere post which will be a hard launching 4-speed car. Normally I would consider 3400#-rated springs with an automatic, but could I magically have the right springs with the 3800# leftovers?

Back in the '70's I spent lots of time playing with springs for my '65 Coronet. I watched what the different Mopar's used and how their suspension worked/reacted.
I would expect that your '66 Coronet would work really well with 3600# springs. But for a '63 with a 4 spd I'd try something like the 002-003 springs. That's a 4 spd spring stack.
With my '65 Coronet I eventually copied a buddy's 002-003 springs except using the stock oddball main leaf (21" front half). Worked great. 550 HP, nearly stick shift like launch with 8 3/4" convertor. Take a good look at the 3000# springs.

 

[fbs63]

In my experience the lightest spring that maintains the ride height you want works the best. Cut the rubber bump stops for the front upper control arms down to about 3/4" tall to gain more front end travel.

 

[66Satellite47]

In my experience the lightest spring that maintains the ride height you want works the best. Cut the rubber bump stops for the front upper control arms down to about 3/4" tall to gain more front end travel.

It's not only the ride height that matters, it's matching the response of the leaf spring/shock combination to the torque that is applied to them. The desired ride height is adjusted by changing the spring arch not the spring stack design.