I jumped onto Sydney Datsun Club's home page and sent them an email so hopefully I'll hear something back. I noticed they have a central coast cruise in their calendar for the end of Feb. That wouldn't be too far to travel!
I looked i into the MG car club. They do some fun events pretty close to where I live but I wanted to find a club that was made up more of Nissan/Datsun lovers.

I was going to attend their next meeting in February (first Tuesday every month at Eastern Creek) but I live about 10 minutes away. Bit of a trip from Newcastle. If your looking at their Facebook page, there must be some contact details. A couple of members here are also members, maybe they'll see this. The only clubs I can think of up your way is the MG Car Club of Newcastle or Westlake Auto Club. They both 'should' have Web pages, & being locals, would probably be just as good for you as a Sydney based club. I know a couple of Westlake members, great bunch of people to hang out with.

What is the best way to contact the club? I am following the Sydney Datsun Car Club Facebook page.

It might be best to talk to the officer at the Sydney Datsun Club about this. At the Sydney Datsun day there were a few cars on Historic plates that I couldn't understand. These were probably the Modified Historic Plates. If an engineers report is needed, they might have a preferred engineer. A friend has a Hillman Minx on Historic plates, he had to take the mags off it to qualify for the plate. I've got 2 Sunny's I know will need engineering when I reregister them, I'm hoping to get them on Modified Historic plates.

When I first heard about the new log book scheme I was given the impression that it was intended to be more open to allow engineered, modified, vehicles to be club registered.
After reading further, it seems to still aply the same guidelines of that the vehicle has to remain close to original.
My 1200 ute is running 4AGTE with most of the driveline and suspension modified. It is all engineered though.
I wanted to know if there are any car clubs that accept modified vehicles for club rego?

My understanding of modified historic rego is if it needs to be engineered for full rego it will need to be engineered for modified rego. So still no easy way to shoehorn bigger motors in legally.

my datsun 120y is with Sydney Datsun Club for 5 months now

what do you mean by modified ?

Was wondering if anyone else has been looking into NSW's new modified historic rego? Also can anyone suggest a good nsw datsun/nissan car Club to inquire with?