Wasn't the JSU-152 ( ISU-152) based on the JS-2 ( IS-2) not the KV-1? Would not the spg version of the KV-1 be the SU-152?
I know the ISU-152 and SU-152 used the same main gun so that aspect is the same.

I'm not that familiar with the differences , running gear -wise between the KV-1 and JS-2, perhaps they are similar enough not to matter.

Jerry