It is very doubtful that the windshields for the 6 & 8 cylinder Dodge Brothers cars interchange in 1930. I am into 1931 Dodges and know a lot about 1930s & 1931s. I will tell you that the 1931 DH6 & DG8 windshields do NOT interchange. There are a lot of differences such as front fender lengths, hood length, headlamp size and shape (more bullet-like and larger on the 8s), etc. If you email me, I can supply you with information for a guy who is pretty much the expert on 1930 Dodge Brothers cars. John at keiser31@charter.net Got a picture of your car to post?
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1931 Dodge Brothers DH6 business coupe wire wheels
1931 Dodge Brothers DH6 business coupe wood wheels (my 1st car)
1967 Dodge A100 compact pickup