I see there are a lot of fans of the 292 on here. I agree it is a stump pulling motor, but if I ever plan on traveling to shows, I would like to have a motor with which I can instill a little more trust in.
No, I'm not going to try to sway you to keep the 292 (which I love in my '63 C20) but I just wanted to say that those engines are every bit as reliable as a 350. It's all down to maintenance and driving style. I do fully understand wanting to have a rig you can run at highway speeds though. My C20 will yank a house off it's foundation, just don't plan on getting anywhere really fast. You will still have to address the gearing issue on your K20, but you are on tack to getting her to highway speeds. Good luck in your search for headers, that's always fun. One of the reasons I stick with stock motors anymore is because I hated dealing with header issues.