to fully answer the original question. it is concievable to put an 060 on the a3640 however...
-the 060 runs on 3.3 volts the 040 at 5 so you would need a votage regulator socket to make the change. only one company that i know of makes such a regulator for 060 and it costs about 2-3 times what the above accelerators do.
-the 060 also has a slightly tigher timing spec compared to the 040 and since the a3640 and a3000d are a bit loose timing wise it is likely to be a problem. 3000t 4000 and 4000t systems and 3000d systems with all new rev. chips with a 3.2 a3640 might be ok
-finally any rom on board or os rom that detects the a3640 specifically and uses 040 specific features may have problems. AFAIK this is not a problem.
BTW a sonnet quaddoubler 040 mac accelerator would put a 50mhz 040 on the a3640. there is also a ram expansion specificly for the a3640 that adds much faster ram although i cant remeber the name of it right off.
