I've seen some old graphics cards that won't work with Windows 95. Maybe you'll get one of them. You'll probably have no L2 cache, no PCI, and 30-pin memory sockets if the 486s are old, which they probably are. Then get a Pentium motherboard and a tower case, buy the stuff listed above, and plug it in. You'll be glad you didn't go for that 486.
Monitors are still expensive.