I think they had wooden wheels back then. Just an Orwellian comment. Wheel size may have varied from model to model as some owners may have preferred a smaller wheel to make it easier to get around in the cockpit while others may have gone for a larger wheel for racing or being able to steer while seating on the sides. The correct size would likely depend on your preference; too large a wheel might require you to stand while a too small one may feel too heavy. Just sit at the helm and imagine a wheel and stretch your arms into a comfortable steering position and then have someone take a quick measurement from the wheel hub to one of your hands. Once you have the approximate wheel radius then take a stick or a line and run it around to see how the wheel rim would fit; at the top make sure it would not obstruct your line of sight, at the sides see how it would feel to walk around it and at the bottom check out clearance for the legs (I like to steer with my feet sometimes and like the wheel rim just high enough to be able to rest my foot on it). Anything larger than 28" in diameter should provide enough leverage for steering while you may go as large as the clearance to the cockpit sole and coamings may allow. Some like the looks of larger wheels but remember that you may be seating behind it for long hours so choose something that looks good but is also comfortable. Take also in to consideration any future plans you may have to install or to replace a helm chair.