I'm posting this here in the hope that what I've done will help someone in the future when installing a new radiator.
I installed a new radiator (from Holms, 3-tube core with my tanks)in my '87 GN. It fit right in although the core seemed a little long as the rubber radiator supports don't line up very well. There are two areas where fasteners will hit and possibly damage the radiator.
1) The stud screws that hold the air-conditioning bracket to the upper radiator support are about 3/16" too long now that the radiator is a little thicker. These will punch into the cooling fins of your new radiator when they are installed. The solution is to cut about 3/16" off each of these stud/screws.
2) The cooling fan is bolted to a metal bracket which, in-turn, is bolted to the sheet metal of the car at the bottom. The bolt heads protrude toward the radiator and will damage the cooling fins and rest against the tubes and possibly cause a leak. My solution was to procure two 1/4-20 x 3/4" Elevator Bolts and bolt the bracket to the cooling fan with a washer and nut with the nylon insert (sometimes they're called stop nuts). My local Ace Hardware place had ugly black ones in stock. I ordered mine from McMaster-Carr, the cost was about $11 for five stainless steel bolts. website: mcmastercarr.com and you can order directly from there.