Mark it's a 71 240z, was it 907 Green originally? It looks like it. The fender mirrors were used up until late 71. If you look at the early girl bingo thread you'll see a Blue 240z (HS30 01428) with fender mirrors remounted on the doors. So I expect it was toward the end of the 71 model life that the fender mirrors were used in Australia. The early console is due to the 71A transmission and the rear vents in the hatch were removed after HS30 00500.
In terms of buyers remorse, that will wear off after you get a couple more paychecks. Then you'll remember it's not a sprint, it's a marathon and there is no rush to do it. You have the space and you've done it once before.
Shame about the accident damage.
However early 240z's like this are quite rare now, if you read the Early Girl Bingo thread it's my estimate that maybe 300-350 (maybe 400 at a pinch) of all 240z's delivered to Australia still exist.
If you can share the exact chassis numbers of both I'll add the early one to the Early Girl Bingo thread and if we at least have a record of the 73 we can keep track of it's situation in future.
PS: I recall seeing your car and you telling me "never again" in terms of restoring an S30z. LOL.... I've said similar things to myself. It's easy to forget how much work it is, but it is rewarding and satisfying.