v8 would be easier than v6 i agree. Not as unique though, in a H series. Don't know how long you have to be on P's or what the restrictions are.. The v8 should be a reasonably easy job, shouldn't take as long, but if you aren't allowed a v8 on p's and you finish the job in a year instead of 2, you are going to spend a year as passenger in your own car. That'll test your patience lol
Those laws are strange.. i think in QLD you can drive a 199kw normally aspirated 6, but you cant drive a 165kw v8. You can drive a 199kw hot hatch too (factory only i think, no mods?) but you cant drive a turbo-diesel 4wd. No more than 200kw, no turbos or v8s. Doesn't make sense, they should grade cars/licenses on power/weight ratio, not the other stuff.
I think the car that you linked to is already overpriced at $2500 and needs $3000 worth of rust repairs. it doesn't even mention options like power windows and suchlike, you can assume it doesn't have any. Its also only a six with a traumatic.
If you are going to fit a modern v8, find a v8 with all the options and no rust for the same money and save yourself a lot of heartache. If you get lucky you may find one with with a T400 instead of a traumatic, that should make it easier to fit the later model engines.
Keep in mind.. panels and paint can be fixed easier than rust. Don't look for the one that looks in great nick but has cancer throughout, get a sound cabin and go from there. Chances are you will be repainting your project anyway, so lack of rust is much more important than it being straight with good paint.