G'day Matt, welcome to the forum!
That looks like a fairly tidy base for a project, although you've got some work ahead of you as far as sourcing parts is concerned, there's not much of the standard interior left in there. Looks like it's seen some track work?
I'm guessing the diff has been messed with as well? If all four wheels are the same size then the rear track looks way skinnier than it should?
Also, that's one hell of an exhaust for a 173! I'm wondering if a V8 and maybe it's 'proper' wheels were removed prior to selling?
I think its original 173 as it has extractors, full twin system and some other work done to the engine, no signs of removal, still has the aircon and power steering pumps fitted.
The previous owner has gone for the A9X look but with what is available in Sumatra I suspect, and the look is what appealed to me, as my plan was to get one when I retire and do a big trip to Australia, but this came up a few years early and was too good to miss.I can easily source a small block Chevy over here to go the V8 route if I decide that is the way forward.
I dont know about the diff at all, I can see handbrake cables have been cut off!
Wheels have been on it some time, they are in older photos of when it raced before the bonnet bulge was fitted.
I may keep it in race spec just to get it on the road, and not worry about interior yet.