Thanks Jerry. I think I'd read similar info from you at isuzupup.com, but I thought there might be a different solution for the diesel troopers.
I looked at a couple of rodeo replacement radiators (visteon #9145) and it seems like they are using the same core (1.25" thick) as in the gasser trooper radiators. Basically, the inlet & outlet look in the right places, but there are less rows of tubes, and the one I looked at had 1.5" hose connections. The two rows of aluminum tubes will have more surface area than the rodeo rad. since the frontal area of the cores is almost the same (rodeo rad: 24" x 16" = 384sq.in., jegs aluminum: 20" x 19" = 380sq.in.) but the jegs rad. is thicker (2.25"). I think I'll try the aluminium rad.
When you've fit them in do you open up any of the front sheetmetal to fit in a larger than stock unit?

Thanks