I need new rear springs for my 70 Challenger for street use and some strip so what should i get !? 4 speed and 505 !

What's "mostly"?????

Sorry my cellphone is crap ro use.....

Depending on car weight either the 33 or 3500 lbs Mopar SS spring and at least the Calvert/Rancho rear shocks. Bag the snubber.

On spring weight, i would err on the light side. Less hieght gain at rest, and more chassis seperation on the street, where traction will be a problem with a 505.
Control rise with good, adjustable shocks.

If you don't want to go w/ Cal-Tracs and their monoleaf springs, I'd look into the Launcher springs...made by Tri-City Competition, Greg Luneak in California.

Stay away from the MP SS springs unless you can find an old set of the good ones. The new ones are junk.

The launchers will ride rough and bouncy on the street. The Cal-Tracs are better IMO and you can back off the preload on the bars when you street drive it to make it more comfortable.

And guys are as fast/faster on Cal-tracs that ladder bars and even in the 1-teens 60 ft. iirc plus like said above, you can back em off for street driving............

Guys have been real fast on Cal-Tracs and they work good for sure, but a ladder bar/coilover setup will be more consistent. Like when I hear people talking about the 3 second 1/8 mile passes on drag radials like it happens all the time...that only happens at radial events w/ CRAZY GOOD track prep.
Or Ron Rhodes' Camaro going 4.30s on leaf springs and a 275 tire.
Like my own car, there are some real fast passes mixed in w/ a bunch of aborted runs due to traction problems.

Unless you have class rules or just don't want to use anything other than stock style suspension, there's no reason NOT to go to ladder bars or a 4 link. Just depends on what you're gonna do w/ the car.
My point is I don't think there's a leaf spring car out there that wouldn't go faster or be more consistent w/ ladder bars under it.

I seriously doubt this applies to the OP and his car. Sorry for straying off the topic.

Agree but it does show the potential that c-tracs have in more "normal" cars like most of us AND some stupid fast big $$$ stuff w/the best of everything.............

Thanks guys ! I Will look at the Cal Tracks then. Any partnummer that you know of for my Challenger from them ?

Go to their website and enter your car.

You may want to ask about the 25" ft. segment and see what they say cos my car hooks n books since I switched from the stock 20" yet some fly with that as well..........

I don't know who makes the SS springs for Mopar now. I bought my 3400 lb SS springs from Mancini around 2008 and they are still on my 63 working fine. I like them because the car rides very nicely on them. I guess they were the MP springs but when I bought them from Mancini they just said they were SS springs on sale as they came with the rear hangers (shackles) and bushings for a nice price. The MP springs may be junk today or could be ok as I don't know who makes them today. If I had the money and I was buying springs today for a street/strip car I would go with the Cal Tracs for sure but I did not want to spend $800 dollars when I got my SS springs for $200 dollars. It would cost $800 or more for me to buy Cal Tracs because I would definetly use their Mono springs that they recommend. And I believe they have different heights for their Mono springs. Good luck to you. Ron