DGN

I just put some Eibach prokit springs on my 99SS and was tight on money so I ordered some take off de carbons from SLP to replace the old ones while I was at it.
I noticed the rear ones that I received from SLP ,that they say are off of z28's are smaller in diameter. They all have different numbers
Original SS rear - R4 ... / SLP Take offs - N2 (thinner)
Original SS fronts - J9... / SLP take offs - EK
I have searched all over and contacted both GM and ACdelco
and they are of no help since these de carbons are discontinued..
Does anyone know how I can get these numbers checked to see what
the differences is... I hope I am no going to mess up my new springs
by running these thinner shocks in the rears..
Thanks for any help...