Internet info I thought interesting. (not sure if all info is correct but interesting)
Plymouth continues its rising sales, just about the only car to do so during the Great Depression. While styled nearly identically to the 1929 Model U Plymouth, the 1930 Model 30-U Plymouths had an "all steel" body. Externally the most visible change is to a wide radiator shell much more in keeping with the industry standard. The fuel gauge was moved from the top of the tank and put on the dash and becomes an electrical instrument. Hydraulic shock absorbers replace the earlier friction type. There were many running changes during production of the 30-U. Early production had a vacuum tank fuel pump. This changed to a mechanical fuel pump and a water pump was added. There were three different types of wire wheels used with three different bolt patterns. Early wood wheels were de-mountable rims while the later wood wheels were removable. On April 8th, 1930 production of the 30-U began with VIN number 1,500,001.
Happy Motoring!!!! - Rich
The nameplate on the radiator shell is different, the engine now has a water pump and an oil pump. Late models had the oval backlight and a center-moutned chrome horn on the tie bar. (The theory behind the ribbon radiator was to give the illusion of a longer hood.)
I have an early 30U. Vacume fuel pump. no water pump. Wood spoke wheels rivited to the drums. All steel body. Round tail light, rectangle back glass, horne mounted between head lights. Plymouth changed all this mid production.
Sorry, since the thread didnt specify "early production", I was just listing the differences that I knew of for all of the 1930 calender year.