[Mr70]

Is that a #914 Fan shroud NPD sold you?..if so keep it.
An 18" diameter 7 bladed clutch fan is what the factory put on it if yours is an LS-6 w/4:10 rear,or LS-5 w/Air Conditioning,or optional V0-1 equipped.
Either the LS-6 #065 or A/C #772 fan will work,as they are near identical in design/function.
I would stick with original Harrison 4 core tanks,then get a new core installed in between for durability,especially if you plan on adding a Vintage Air system in the future.It will pay for itself in the long run,regardless of which direction you plan to go with on the car.