Mine is a bit smaller than you are after but I have the front of a power steering unit sitting on one side of the radiator and I wanted space for wiring and the prop rod on the other side. Off the shelf radiators are way cheaper than custom radiators so this is the off the shelf one I came up with that provided clearance for the power steering unit, the prop rod and the wiring harness.
Griffen Thermal Products, Chevy style, Part # 1-25241-X.
Overall height 15.5”,
overall width 27.5”
Top outlet tube, 1.5”
Bottom inlet tube, 1.75”
The radiator sits on top of the front cross member and not behind it as stock. I use a Bosh electric pusher fan from a V8 Mercedes (junk yard special).
Picture below is earlier radiator with same outside dimensions The Griffin radiator has cap on other (passenger) side.