I did a search and it seems like " All American Models " had a 300G model and not Modelhaus. Unless they both had one.
I found this post from a guy named Gordon :
I got my resin copy of a '61 300 the easy way....I ordered it from All American Models. However, that was 16 years ago (and I still haven't built it!). It's supposed to use the chassis from the JoHan '62 300, but technically that shouldn't work since the '61 had a 126" wheelbase, while the '62s had a 122" wheelbase. The JoHan '62 chassis does fit the AAM '61 body, however. -Gordon