Upgrade 65' Impala belts, headrest?

[monza]

Looking to see if anyone knows any upgrades I could do that are easy and possibly reversable/removable for my 65 Impala SS #'s matching car. It's a sunday driver with low miles and I don't want to change much. Has only a lap belt, no headrest. Can I add a head rest and only have a couple of little holes for each headrest. (cringing still at that thought) The belts, any options out there with out messing up things up?



Thanks

-it is getting farther from #'s matching but I have all the correct parts to change back or sell with the car.
-upgraded transmission
-disc brakes
-new carb
-electronic ignition.