The Wagon shocks have a bit more travel. While I qualify this with "do at your own risk" I have used the sedan shocks on my '73 wagon.
There is about 1-1/2" more travel in the wagon shock. You can compensate for about an inch of that just maximizing the threaded portion of the shock. I used three of the bushing washers between upper end of the shock and its corrosponding lower bushing. I then used a tubular spacer of about 5/8"-3/4" on the lower end of the shock and its upper bushing washer.
This effectively made the shock about 1" longer. I have not had issues missing the 1/2" of length. Nor have they bottomed out on me due to limited travel. There are also extenders you can purchase. Just don't put too much "extention" on the top of the shock or it can bottom out. Unless your one to fly over rail road crossings, over extending likely would be less of an issue.
Anyway, for me it saved the hassle of finding and paying for the stock dimension shock.
Tom