I sort of get where you are at but what is bang for buck? Best profit, most enjoyable drive, easiest to restore, intended useage ??? Means a lot of different things to different people. My old unimog is a real gun off road vehicle as long as you are happy tooling around at no more than 60 KPH. Most of the late 60 / early 70's "Supercars" or their lesser and more affordable siblings (to meet your price) are dogs to drive fast. My old 3.8S Jaguar was a great car for it's day but getting the parts to restore one without selling your first born is a big ask.
With the various import restrictions in place you would have to say that it would likely need to be an Australian delivered car to fit your price cap. How about a V6 Ford Capri to open the conversation? The RS2600 for example. The RS3100 is way over the limit.
C5 RS6: Sportec, Milltek & Wagner -- B5 RS4 : modified -- B5 Audi 1.8 quattro 132 Kw -- 2007 VW Touareg TDI -- UNIMOG 404 TLF8