You'll need a boss/hub for an aftermarket steering wheel.
Seems like most people are using the Grant hub #4581(
http://tinyurl.com/5c4uu7 ).
You'll need another adapter to the Grant hub if you're using a
Momo/Nardi wheel or any steering wheel that has a 6 bolt pattern.
I've heard
Momo kits for 510/240z work. No personal experience. I did contact this seller(
http://tinyurl.com/562b3t )
asking if
Momo kit #3503 would work with a Datsun Roadster and he said it would.
I've purchased this kit(
http://tinyurl.com/6gtxqb ) and the hub does fit on the steering shaft spines.
My Roadster isn't running so I can't give any real comment of how well it works.
The construction of the hub itself is similar to a
Momo hub but the cover is cheap.
It's a plastic type material, not like the rubber type matterial
Momo uses.
But it does have the dual 6 bolt pattern so you can fit a
Momo/Nardi wheel to it with no problem.
Hope that helps.