This will seem like a trivial detail, but I have a pet peeve regarding junk door-lock buttons. As small as they are, they're also the most obvious door item, and for some reason, on older cars, they've often been replaced with either the wrong type or universal parts-store wood junk. When the wrong buttons are used, they can bind and rattle in addition to looking lousy. New ones are offered for lots of popular cars all the way back to the '50s, and they can make a big difference in interior feel and function. The lock buttons on this '67 Camaro actually serve to guide the mechanism; new buttons and new ferrules are the best few dollars you can spend.