The biggest issue with a Nitto stem IMO is that you're likely t have to sand it down to fit the steerer. It also doesn't quite look period correct, but I'd worry much less about that. Neither one would bother me much, as I have a sanded down Nitto on my '72 Grand Record.

You're options for seat post will be a bit limited by the uncommon diameter. You can get a cheap Origin8 on eBay that looks OK if you remove the logos (easily done), but a Campagnolo post would look nicer (again describing my own choices).