The voltages may be different. Some chips like 5v, others like 3.3v. Make sure they're the same voltage, and they should work. Check for jumpers, too. Some may have an SX/DX jumper or a DX/DX2 jumper.
Do a bit of homework. The DOS card will work with all 486 processors but not all 5x86 processors. There is some really good information about upgrading DOS cards still floating around from when they were current.