Personally, I think the racks look cool on 914s. But they can block cooling air from getting to your engine, so a lot of folks pull them off since they really should not be used.
If you intend to use the rack, I'd go with bolts (and find some thick skin here for admitting it
) If it is just going to be decoration, leave it as is. if you don't like the way it looks, pull it and fill the holes after clearing out the rust that is bound to be in there.
Zach