If you look at the instruction sheets for the LUV trucks, located in the technical section, it will show you where to trim for the 22 x 19 inch two core aluminum radiators. Also some pictures on
http://s731.photobucket.com/albums/ww314/OldRob/Another option is to put a heavy cap 22 lbs on the radiator and use an inline filler. Use a 18 pound cap and a coolant recovery tank which draws to and from the radiator, that has the radiator connection on the bottom.
The brass radiators from the 70's were 3 row 5/8" tubes, CES design, built by a major radiator manufacturer. They were designed bolt in to fit in the original opening of the 76 thru 80 trucks. They were down flow and had a goose neck filler. Also they worked on the V8 A/C trucks.
A stagered 7 blade fan was used as it provided the best cooling at idle and speed. One problem that even spaced fans have, is at speed the blades flatten and it acts like a solid disk, blocking the wind flow. You will notice that most factory fans of size are staggered, with fan clutches. In most vehicles, fans cease to help at approx 40 - 45 MPH. In fact if you live next to the freeway and work just off the freeway you could commute to and from work without on. (As long as there is no tie ups).