I had to agree with Bill, the reference to a GM base and the somewhat odd (no, I didn't say crude) looks made me think Holden, which led to a rather lengthy web search . . . there are a LOT of Holden specials! I finally found it (I think):
It is Australian, and was built by Bill Nevid in the late 1960's (1968-69). It's based on a Holden EK, with a lot of other odds and ends thrown in.