the car is on heritage rego at NSW. is it transferable to me who resides in Vic?
Nope; not transferable. You will have to arrange new historic rego in VIC.
if not able to transfer, how can i legally drive the car back to Vic?
With an Unregistered Vehicle Permit. In NSW, you must sign a declaration that the vehicle is basically roadworthy.
any idea how to tackle rusted holes on side panels and in doors?
Carefully, and skillfully.
If a vehicle travelling on a UVP has a lot of rust, expect to be pulled over often and hassled. If the car is truly a shitbox that shouldn't be driven without a lot of work, the cop may decide it's dangerous and will red-sticker it, insist it be towed, and give you a huge fine.
The honour system works really well as it is at the moment, and it shouldn't be abused.
any DIY tips in fixing both interior and exterior cosmetics?
Varies a lot with vehicle.
Would love to hear your interstate purchase experience and tips you'd love to share.
On UVPs so far, I have driven -
a rough-looking 1974 142 from Bridie Island QLD to Blue Mountains NSW - I was pulled over twice, because the car had patina and it looked a lot rustier at the time than it really was a very clean 1973 144 from central Victoria to Blue Mountains NSW - cops never looked at itan untidy 1974 145 from Yass to Blue Mountains NSW, in the middle of the nighta 1987 740 Turbo wagon from Newcastle to Blue Mountains NSW, also in the middle of the nighta clean 1988 780 from Canada, straight off the ship and the Botany docks, to Blue Mountains NSW - got pulled over in Woodford and the cop got confused because he went to the RHF window to ask me about the lack of plates, and the car was left hand drive
All the cars above had seat belts, working lights, indicator, horn, and brakes, the tyres were all in reasonable condition, and none had plates. The UVP paperwork was visible and the big yellow UVP sticker was visible on the windscreen. I stuck to the approved route on the UVP and didn't deviate from it. So if/when I was pulled over, the cop inspected the paperwork and had no cause to hassle me.