My own experience with A/UX is that it does not like standard 68040 PDS cards. My Q950 will not boot in A/UX with a Daystar Turbo 040 accelerator (40MHz with 128k cache) installed. Your 601 card has 1MB L2 cache onboard, so if A/UX could recognize that alone, things would be interesting.

Dedicated 040 PDS L2 cache cards, which would be the "right" way to do this, are scarce as hens' teeth.