No worries, I could be wrong and the US parts will bolt right into your 620. Otherwise you could use Stanza L16 brackets or 200B or Bluebird brackets.

Making an L-series crossmember is one of the easiest kinds. There is an overview with photos in our tech article L/Z/KA/SR Crossmember shows how to for the 1200. It's basically two square plates at 30(?) degree angle. Many photos of different Datsun insulators that swappers use to get slightly different install heights