I want to change my steering wheel, but i have a very old car. How do i know a new one will fit?

My car is a 1970 Mazda 1800, which has its original steering wheel. I just want to put a new wood style one in that has a smaller diameter. If i buy one off the net, or a wreckers how do i know if it will fit?|||most of these you have to buy a hub adapter to get them to fit. unsure if they make them for that one , Search here for one http://www.grantproducts.com/|||best and safest is to go back original.|||You will need an adapter that will work with your car. Steering wheels are application specific. Your local auto parts store can help you. GL