Hello from Colorado. Nice to meet another mid seventies Airstream owner. I have a 75 Overlander 27' that I am working on this winter. I found it in pretty good shape last fall, but it suffered from the common "rear end separation". I've repaired that and I'm lucky I have no frame cracks or buckles. I'm installing new, bigger wastewater tanks, new axles, new plumbing, new water heater, and new fridge. $$$$. I find this old Airstream pretty well built, especially the aluminum extrusions used in the interior cabinetry. Should last a very long time. I like it.
Mine does have the common front window "rock guard". I think they are readily available. I'll bet someone with chime in with a link to a potential source.
David
Here is one from Inland RV in California:
http://www.inlandrv.com/catalog/index.php?cPath=71