My radiator has two bushings (one threaded into the radiator, the other threaded into the first). I am guessing if I took those out, the threads would be approximately 1/2". I would think I could plumb 1/2" lines from the oil filter adapter to the radiator. Seems to be that would be "big" enough.
Bill
'85 F350 2wd C&C electric/hydraulic dump converted to 4x4, Dana 60 kingpin 4.10, DRW Dana 70, 460, T19 4sp, B&W1345, 3G
'06 SuperDuty 6.0 (The Bird Doggin' Rig)