This list of [CPUs and their sockets][1] shows you would be limited to two very historical CPUs indeed, the [8088][2] and [8086][3], if you use a DIP40 socket.  

Neither of those are 486-based, nor will they will execute the full 486 instruction set. To run the full 486 instruction set, you'd need a PGA socket (of which there are many, listed in the first link in the first sentence) or a slot (op cit.). 


  [1]: https://en.wikipedia.org/wiki/CPU_socket#List_of_x86_CPU_sockets_and_slots
  [2]: https://en.wikipedia.org/wiki/Intel_8088
  [3]: https://en.wikipedia.org/wiki/Intel_8086