My A3000T also has the onboard 68030 like yours (Some A3000T-040's did not).
When I changed mine over to use a rev 3.2 A3640 board in the fast slot I remember changing some jumpers to get it to work, and also adding the 74F08N (there is another jumper for that if it's installed as I remember). I don't think the fast slot will work without these jumper changes. The National Amiga Technical pages was the source of this information for me as I remember. I'll try to dig it up if you need it.
Sorry if you know this and have tried it already. PS I also had to upgrade my Roms and make sure the memory was all static column if I'm thinking clearly (this was over 10 years ago :-D)
Good Luck,
Jeff
