I believe your motorhome, MDC99's and mine use the same Amber and Red lenses. Like MDC99 said, Monacos products around our year and models use the GM Blazer and Full-size Van Red tail light lenses. The problem I had was the Amber lenses. I had a broken one when I got the motorhome. Had to order the correct part number (L or R)thru Monaco because the GM Tyco lenses were not available thru any other vendor--yikes--not cheap, but worked out OK.
If you notice, the Amber Lenses (turn signals)and their lamp housings above your Red lights are inverted and swapped. In other words, at the factory Monaco inverts the Amber housings and lenses and inserts the Lamps in the Amber housing in the second lamp socket (There are 2 sockets in the housing that will take the factory lamp socket) Then swaps their position. If you notice, the Left Amber lense is inverted and is marked RH. The Right amber lense is also inverted and marked LH. That is why it was so confusing when I had to order an Amber lense. Glad I got the correct one. This is the normal configuration from the factory. I didn't like the looks of the factory setup, so I swapped them back onto their correctly labelled positions by swapping both the lamp housings and lenses, and re-positioning the lamps into the other lamp socket. A nice result of this is that your turn signals are easier to see from the rear now. They seem abit brighter to me.
02 Monaco Diplomat 38PBDD w/GE Resident. Frig, Anti-sway, Bilsteins, Flat screens. 08 Chevy HHR Toad. Onboard= 3 lb. Teacup Chihuahua "Nugget"