Need help with super stock spring sag

I bought my 70 Challenger with the Mopar s.s. springs already installed.

My problem is that I think they are sagging. Is there a way to tell how high the car should sit when they are new or per spec?

I measure 27.5" to the top of the wheel well lip with 275/60/15's. The car, to me, looks like it is sitting lower now than before. I have had the car 12 years and used to be able to get 295/50/15 installed no problem but now they are close to rubbing on the wheel well flange. Also, I can no longer get the pinion snubber locked in to the top hole.

I hate to drop a couple hundred on new springs if I dont have to. Currently the car runs 12.9 second quarter with the existing springs and tires.

Any help? If I do have to get new, any suggestions on what to get? I do like the rear end in the air.

Could put longer rear shackles,that will raise it,sounds like it may be time for new ones after 12 yrs, best to go to local Chrysler dealer and get ss springs, was cheaper that way due to shpg....

It depends on the part #. Except for the 002/003 springs they all sit pretty low. My friend just bought new 456/457. They didn't raise the car or pick-up 60 ft.
Doug