E30 Zone

I have some secondhand springs, the rear ones are lowering springs but Im not sure about the front ones. The only writing on them is;
GMAX 30 BM 13 Rear
and for the front TERRA 45 034 VR
I also have two rear shocks, which came with the rear springs, with the following written on them;
Bilstein BNO-1981-HE236
Can anyone give me some idea what all this means please?
Not sure if its such a good idea to mix springs (front to rear) or not. I am hoping that it is possible that they can be identified from the writing on them.
Any ideas anyone?

hey Gonzo-the-Great
not sure about the gmax springs, but i also have the Terra 034 VR springs. The terra springs are soft with usually about a 45mm drop from standard, and with mixing the springs, not sure about that

Mitchell