(my bold)
If you'd really prefer LHD, I can't see you valuing the RHD properly, let alone the seller. Maybe it's not the car for you? Some RHD-specific and Japanese market-specific parts are far harder to source than the equivalent LHD parts, and if you were to find that too annoying then maybe your heart would not be in the car?
My ha'penny worth: On a global scale, and comparing like-for-like in condition and level of modification/originality, a 1972 Fairlady Z or Z-L is going to be something like 20% to 30% more valuable than a 1972 HLS30U Datsun 240Z. A 1972 Fairlady 240Z or Fairlady 240Z-L maybe 30% plus, and a genuine 1972 Fairlady 240ZG maybe 60% to 70% up on the HLS30U. If the cars were in Japan, even more so. I own a few of these cars, have been watching the global market for 30+ years and I think I have a pretty good handle on what's what at the moment. I have seen USA-based marque and model 'gurus' and 'experts' talking down the Japanese market models for many years, but mostly they are talking out of their hats and know next to nothing about the cars themselves, let alone the global market situation.
Having said that, it's a case-by-case situation. Less than ideal location and somewhat under-the-radar selling will not help the car to achieve its maximum potential. Put it in front of the right people in the right place, get a few facts straightened out and it could do well. This could be to your advantage. If you play your cards right you could buy the car for much less than it would achieve elsewhere on another day. If you can effectively 'snipe' it, you could probably move it on for more than you end up paying for it if you found it hard to live with.
If you have any Fairlady Z-specific questions (specs, equipment, originality etc etc) I would be happy to try to answer them to the best of my ability.