I have a 1963 C10 with an inline 230 engine. I also have a 1965 C10 that originally had a 230 engine. Both had lower radiator saddles on the lower flange of the crossmember. The original radiator was tall and narrow if the engine was a a 230 (not sure about the 292). The V8 engine trucks used a wider but less tall radiator with lower saddles on the upper flange. Your frame will have the holes in the upper flange in the right place for the saddles. I’m happy to report that Champion Radiators sells a pretty much bolt in aluminum tall narrow (6 cylinder/ lower saddle position) radiator that has worked great for me for at least 6 years. No issues and it handles the SC heat with zero problems. My 1965 C10 now has a 283ci SBC with a wider radiator. It’s less tall than the Champion radiator and won’t fit between the frame rails. The lower saddles are on the upper flange of the crossmember. It uses a different upper radiator hold down bracket than the inline six radiator.
