Ive searched and couldnt find an answer anywhere.The C70 is designed off the 850 right? Do coil springs for the 850 fit the C70?

Yes they will fit.
But I believe the C70 is heavier springs.

What are you trying to do?

lower my 01 C, and I was going to search ebay for some used 850s springs

Ok that should be fine.
If you had wanted to stiffen it up or raise it a hair I was going to say buy XC70 springs.