Porsche 914s were typically delivered from the factory with either Mahle or Fuchs wheels. Fuchs seem to be the preferred racing wheel for both 914s and 914-6 or 914-GT race cars due to wider set-ups. A large fitment is possible on a GT body so oftentimes these cars can handle a larger Fuchs wheel such as a 8" or 9" inch wheels. The Fuchs wheels are lighter than the Mahle wheels so that's another advantage to using Fuchs for sporting purposes as the lighter wheel reduces unsprung weight.
Following are some pictures of 914 wheel set-ups - some fitted for racing and others simply for show.
Fuchs with Frosted Black look:
914-4 wheels in show condition:
Wheel choices on your 914 really come down to the preference in look and utility you're going after. If you are after a sporting purpose car you may be better off with a Fuchs alloy wheel which can run much wider than some traditional wheels that came on the Porsche 914. Be ready to drill your hubs or refit them if you're going with Fuchs on your 914-4 as the 4-cylinder cars came with 4-bolt pattern hubs as opposed to the 5-bolt patterns on Fuchs alloys.