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 archive is not complete but it's enough to give you a good idea of the amount of work involved. The last changes I documented should be available under
http://www.amibay.com/showthread.php?t=13965
