About 11 years ago I built my own Zorro slot for the 500 and used a ZII GVP SCSI/Memory card to run a BBS. Worked great until the GVP card died 3 years later. The expansion I built required one logic chip added to take care of some kind of buss polarity or busy/ready signal. I did not wire the expansoin card to a logic chip on the motherboard as you mention with the 74ls32. I added the extra chip to the card I built. I got the info/schematics from aminet. The doc is still probably out there. Now I'm going to have to dig that old card out and have another look after all these years.
Here we go, this looks like the doc I used. It lists a 74ls86 as a required part. That sounds about right.
http://main.aminet.net/pub/aminet/hard/hack/2000slot.lhaPlaz
