A review said it has an AT board, and it is 1995 vintage. ATX came around about 1997. Here is a link to a picture of it.
I'd go for a new ATX case and power supply since that is the form factor for most new motherboards. I've seen inside one of those old cases, and they really have stuff crammed in; no fun to work with, and expansion slots are limited.
He could buy a keyboard for not much more than the cost of a plug adaptor.