If a single pass is what you want then look for Fedco #2-342 core. 9 1/2" X 6 1/8" X 2"
GDI # for above is (If I recall right ) 399010, but I"m not sure of that.
Core comes from a chevy pickup with air 69-72, and that I am sure of.
I'd strongly suggest you avoid cores thicker than 2" as the resistence they offer is more a hinderance than a help.
As Bob points out there is a wealth of info here on many differant rads of all kinds.
Good luck and welcome to Pro Cooling.