Get creative with your photo-shop software.
Lots of big truck steel bumpers you can mock-up and decide what you like the look of on that coach.
Entire headlight replacement fixtures are readily available, as noted post above, from the vintage truck sources. There are also busnuts doing the reverse, buy their old round equipment used.
The front skin angles on that vintage always looked funny. Stripping that and blending it into your new headlights and bumper could be a lot of fun!
Happy coaching!
Buswarrior