Momo has a hub for the 1st gen, no problem. I'm not sure if it's still available, but I think it shouldn't be too hard to find something suitable. I have one extra (brand new) somewhere, but wouldn't have a clue where I've put it, after moving to my new place.

 

All RX-7s (and the REPU, RX-8, Mazda6, etc.) share the same spline. I have an RX-8 wheel in my first gen and a 1st gen wheel in my REPU. Regardless, it's a simple thing to weld a hex stub on the end of the shaft for a standard quick release with the MOMO 6-bolt pattern. That's what most of the race cars do. This also has the advantage of moving the wheel toward you, for better leverage. And, if you have better leverage from being closer to the wheel, you make up for lost leverage from using a smaller wheel. I personally prefer the standard size wheel (same size as the RX-8 wheel...no ones calling that a "school bus") but am unhappy with the sloooooow steering ratio. The options are power steering box (with or without assist) or stepping up to a Rack and Pinion swap.

 

I just bought a hub adapter at Pep Boys for my Grant wheel about 6 months ago. Pep Boys sells a different wheel from Grant, but it is a copy of the grant and the hub is the same. Cost was around $18 US. I have a Black and Silver 3 spoke Signature series Grant and love it. Only problem is like others have said, hard to see the tach and speedo.

Later,
Bill.

 

6' 4" here and I do that all the time.

 

I bought my Grant AND adaptor from Pep Boys as did my boyfriend w/ a 1st G 7 - a year later. My mechanic at the Mazda dealership installed both w/ no problems. I did find that the center nut had to be tightened periodically or the wheel would "notch" over on hard turning.