I investigated this matter 7 years ago and concluded the complex logic required to make a 68040 to 68030 bus protocol adapter would be impractical (but not impossible). So I proceeded to modify the A2630 to run at clock speeds up to 52 Mhz. The last changes I documented should be available under Aminet/hardware/mods/A2630Speedupfix.lha. If you have a 50 Mhz 030 and want to go faster leave me a message and your email address. The more recent (but incomplete) document describes the 52 Mhz changes.
