I'm using a Summit Universal PN SUM-380431. It is 30.875 in. Wide, 19 in. High, 2.875 in. Thick and fits like a glove. The radiator will need to be trimmed of its edges on the top and bottom but this was easily done with a jigsaw.
To mount it I took the oval rubber bushings and cut them down to about 1/4 inch in thickness. I placed the radiator down on the rubber bushings and used the rubber piece that was in place on the top of the old radiator to act as a bushing on the top of the new radiator. I then took a piece of 3 foot by 1.5 inch wide piece of aluminum bar stock (from Home Depot) and bent it into a bracket that I attached across the radiator on either side to the radiator frame. This provides a solid mount with no movement. I mounted the fan by drilling two holes through the shroud and the aluminum brace. Tightened with nuts and bolts (watch the clearance). I also added two of the plastic through radiator mounting tabs to the bottom of the shroud for additional support.
I'll post some pictures tomorrow.
The radiator fills nearly the entire space so no shrouds need to be constructed. All in all it makes for a great fit.