Will GM 200r4 work with factory floor shift location?

Got it. I checked the actual dril bit sizes that match closest to the measurements and found a 7/32" (.220) drill is the current hole size for the fittings on the 200R4; and the 1/4" drill (.250") should be equal to the inside diameter of the 5/16" line size, right?

There is a significant difference between the two sizes, but I'm now lean toward the method you used, mating the two fittings, silver soldering them and then trying to carefully drill them out, first with the next size bigger drill and then with the 1/4" drill. I'll also drill out the current fittings on the 200R4 to the next size larger, because it's only .220" now. I'll make an extra set to experiment on and post the outcome. It will save the expense of up-sizing the lower radiator tank cooler.

Last year I bought an old school silver soldering kit, the real stuff, from a welding shop. I used it to solder a larger 3/8" return line into my fuel tank pick-up. A small spool of the solder and a small tube of the liquid flux was $50. It's like nothing sold in the hardware stores these days though. It's super strong!

Sorry for the lousy focus on the soldering example.