History
Not too sure yet, i've only recently acquired it.
Regarding the different vinyl roof design, i have heard there was a dealership in South Australia who were almost the only ones ordering these particular roof designs. I have only seen pictures of the same style design on some Kingswood sedans & a Valiant hardtop.
Modifications
According to the ID tags, it was originally a 6 cylinder vehicle but has been converted to a 253 V8.