Hi Doug, I agree with Silversleeper. It's your coach and it's your choice regarding the exterior vents. You need to be happy with all aspects of your Airstream. Make it yours!
Some vintage owners choose to keep them including myself. There is no advantage to keeping the old vents, it's just a choice on appearance. If you decide to replace them with updated vents or access panels, keep the originals stashed somewhere if you have the space. If you ever decide to sell your Safari, many potential buyers would appreciate having them back.
I'm still using my 1960
Bowen water heater. It works very well, but know I'm facing replacement very soon with the burner tube slowly rusting. If you have the resources and the opportunity to replace yours now, go for it. You will have to eventually and parts aren't available. Like others have said, it would be easier now and you won't chance failure on the road.