More important you also need a 040 socket to solder onto the board cause soldering directly on the chip you are going to use is a nono. ;-)
A 040/40Mhz chip could possibly be upped to 50Mhz but it's always risky with those hot 040... make sure you got plenty of cooling.
One last thing... with a socket and extra cooling on the overclocked 040 the card would take up even more space so make sure there's room for it all. :-D
