I have the same setup, 50MHz GVP A3001 and GVP HC+8
I have an 80MB IDE drive that was originally included with the A3001 but that is the ONLY drive that seemed to work with it. I tried some larger (400MB-2.5GB) WD, Seagate, and Quantum drives without success. So I disabled the IDE and use a 2GB drive attached to the HC+8 instead, it's faster anyway.