I too have a 1977 Argosy. I want to replace the lighting as well with something more modern (please don’t bash me for modernizing) but I’m not finding any advice online either. Most of this stuff seems like it’s gonna be a trial and error type thing. I’m following for advice too but I’ll let you know if I make any more head way in the meantime.
Really favoring this look:
LeisureLED 5 Pack RV Boat Recessed Ceiling Light 480 Lumen Super Slim LED Panel Light DC 12V
4.75" 6W Full Aluminum Downlights, (Natural White) https://www.amazon.com/dp/B077Y78SV4..._lWFsCb5H2GPVK