This might sound nuts, but turbocharge the 292. You can do it on the cheap if you do enough research and shop around. In all reality it's not hard to do. This way you keep the 6, keep the gas mileage of the 6, but when you NEED power, it'll be there. Do a few web searches on the subject...

49 Chevy 3600
65 Chevy K10
66 International 1300 dually 4x4
46 Ford 1/2 ton
76 Tucker Sno-Cat 1642
96 Dodge 3500 Cummins dually flatbed x-cab 4x4
06 Jeep Wrangler LJ rock crawler
If you can't fix it with a hammer, it's an electrical problem