Steering wheels... Since I have suffered through the madness of three, and still change mine once in a while, I will share my lessons learned... Hope this helps.... And sorry for the long note In advance.
removing/ replacing your wheel will take little mechancial skill... Just a deep socket ( depending on the nut installed in your car), a hex set and a long pin to remove your horn button.
Assuming you don't already have a Nardi hub and are staring from scratch.... you do need to know what steering shaft you have installed in your car as this will determine the hub size adaptor you need to buy. I have a VS, so I just needed to determine if I had a 1960-1974 1/2 or 1974 1/2 - later.
nut and column spline sizes:
25mm diameter course spline on 1949 to 59 cars.
21mm diameter fine spline on 1960 to 74 cars with 27mm nut.
18mm diameter fine spline on 1974 on cars with 24mm nut.
Pictured-
1960- 1974 = larger spline ( right)
post 1974 = smaller splices and tapered head ( left)
Once you have this, it's time to shop for a hub, steering wheel, horn button, andhorn adaptor ring. Nothing more required.
I shopped for my hub and first wood wheel at ISP west (http://www.vwispwest.com/GA-64-0154PY.html ). they list dimmension details and part numbers for hubs( both Nardi and their custom ones)
Not only do they sell the standard Nardi adaptors ( same price as most retailers), but also really cool in-house billet hubs that look great and fit Nardi/momo standard bolt paterns ...
They also sell complete kits (wheel, hub, black horn button and horn button ring). The horn buttOn badge I purchsed from Stoddard... It's a 356 hod crest Badge.
Kit I purchsed link-
http://www.vwispwest.com/AP-3053.html
Best to call them... Their web does not reflect all their options...
my car originally came with an Ivory Banjo wheel with an ISP hub, then I went to an ISP West Kit - Custom billet hub/15" diameter with 1" dish 21mm grip wood wheel/ ISP horn button ring adaptor ( next two pictures)--reference above link... So all I had to do was remove my banjo wheel/hub and install the new one. next two pictures.
... Painted part of the hub Ivory to match my blinker assembly. Steering shaft remains black.
Then decided to have Mike Lempert make me a NardI style wheel ( same 15" diameter and thin grip as the ISP wheel, but flat Nardi style..... AWESOME working w/Mike and wheel! http://www.pbase.com/mdlempert/wheels
Unfortunately I specked it wrong, and could not use the ISP hub/horn button assembly I aleady had, so I had to get another ISP hub to fit a Nardi bolt patern and horn button adaptor ( horn button adaptor from Carey Hynnes- Special Edition/Bek, horn button is a hub cap badge purchased from Stoddard attached to the horn button Carey provided.
ISP hub with Nardi/momo bolt patern-
next two pictures are of the Lempert Nardy style wheel- 15" diameter, ~21mm grip -with ISP made Nardi bolt patter size hub, Careys horn adaptor, and porsche crest hub cap badge.
To keep comfortable spacing between the wheel and blinker arm, I added a 1" spacer between the wheel and hub. (in polished aluminum, shown with a 1.5" spacer which was too big for my taste.)
Last two pictures are of two horn buttons installed on the ISP wheel/ISP horn adaptor ring set up. I made horn button with Porsche 356 hood crest I purchased from Stoddard. Attaching to standard black (aproxx 81mm) horn button used in banjo wheels (two sided tape, clear epoxy and some elbow graese)
After three iterations.... I wished I could combine the large ISP hub with grooved horn button ring part with the Mike lempert wheel.
I'm considering selling my Lempert wheel set up ( including horn button, hub and spacer). And have Mike make me another wheel... one that fits the large ISP hub/grooved horn rig part. But that's way down my list of things to get to... I have already spent too much money/time on this... It's the madness.
Hope this too long a post helps.
luis
Picture re of the larger ISP VDM style 9 bolt hub/horn ring that came with the ISP wheel kit.... Before I paunted Ivory.