Wolf_n_Kat -
No problems, I've been busy also.
As Leeann indicated, that plate is exactly what we've been talking about. At this point, the only reason to keep searching for the VIN stamped in the frame is to verify what's on that plate. As I cannot think of any reason someone would swap plates, you can stop here and assume you have the information you need.
Something to consider ... when your motorhome was manufactured, Dodge (and the industry) was trying to deal with the oil embargo, competition from overseas, a drastically changing market, and competition between U.S. manufacturers. Likewise, motohomes were an emerging market that was rapidly evolving and had little technological history (i.e., lessons learned) to draw upon.
The result was a lot of turmoil that makes it difficult to create a thorough database, especially when parts companies tend to see (older) motorhomes as a niche market not worth a lot of investment.
Finally, parts stores like AutoZone, O'Reilly, NAPA, and others cater primarily to automobiles, pickup trucks, and vans, with an emphasis on late model vehicles. The CarQuest store I worked at was unique, starting out as an independent store catering to commercial customers rather than the general public.
Prior to the early '70s, virtually all manufactured motorhomes were Class A, primarily using the Dodge P300 chassis, which is a stepvan intended for commercial customers. I've been told Dodge came up with the M300 designation because some people were upset when they found out their motorhome was built on the same chassis as local bread and laundry trucks. Other than the designation, P300 and M300 chassis were identical.
I remember considerable media attention and discussion when Dodge came out with the B-series vans in the 1971 model year. Similar media excitement surrounded the Kary Van when Dodge introduced it in 1973.
The Dodge B100/200/300 were complete vehicles with van bodies. The CB300 and MB300 were incomplete chassis, sometimes called cut-away chassis. As with the P300 & M300 chassis, the CB300 and MB300 are effectively identical. For the most part, differences are primarily limited some of the CB300 options (passenger seat, radio, etc.) being standard in the MB300 chassis.
To break down the model designations, 300 indicates 1-ton light duty truck, B indicates van chassis and cab/body, C indicates commercial market, and M indicates motorhome market.
So, have your parts store look for a CB300 listing. (CarQuest's database doesn't have a MB300 category, although older paper catalogs did.) If they don't have a CB300 listing, have them try the B300 listing and chose the heavier duty parts when several alternatives are available.
As with all vehicle work, compare the new parts with the old parts before installing them. (People at every step of the supply chain can make mistakes.)
You might have better luck finding a parts store that caters to commercial customers, especially those with medium and heavy duty trucks. (They're usually located in industrial areas and often lack the fancy signs and storefronts common to automobile parts stores.)
Just don't tell the counter people you're looking for motorhome parts ... their brains tend to switch off when they hear "motorhome." Instead, tell them you're looking for 1974 Dodge MB300/CB300 parts.
If, after trying to find the parts yourself without any luck, let me know and I'll see if I can find the right part numbers.
