If it can get a consistent 12-15 and not drop into the 4-8 range that wouldn't be bad. From what I've read these engines have a very flat torque curve and that is what I'm looking for. Horsepower means nothing in a truck unless it's for racing, and I don't race anymore. I'll cruise 70-75 if need be, but no more 80-120 mph runs for me.
I can get 12-15 with the 350 that's in it right now, but on grades it really seems to lack the torque to pull the grades without mashing the pedal to the floor. I hate seeing the vacuum gauge at or below 5, I like it to be at 10 and above. I don't run my engines in high rpm ranges, so if I can get the truck setup to where highway cruising is in the happy-spot of max torque that should yield decent mileage. In my brain and on paper it works out that way, real-world can throw curves at us though. Of course the engine has to be tuned-up and all, which I can't stand it when my rigs run like crap, so it will be tuned well.
In 2015 I had the opportunity to get a '66 3/4 ton that had a 292/sm420/4.57 already in it. I was excited to get it, there was little to no rust, it was pretty much unmolested, and I had never had one with a 292. It would have been easy to install the parts I already had for better mileage and improved stopping power. I got the money from my credit union, and was figuring out how to get it when the guy backed out of the deal. I was mad because we were in constant communication, I was doing so to let him know I was in fact interested and when I could come up to get. He was about 5 hours from me. Anyhow, he said I wasn't interested in the truck and wished me luck finding one. That's what made me angry. As it turned out I found one locally, a little more money, but he was the 2nd owner, and it is a pretty good truck. He said it had a 283 in it, but I knew it wasn't by looking at it. It was gutless when I got it, he had the vacuum advance on the wrong port, the timing was off, and the carburetor wouldn't hold a setting for more than 20 miles, and it had a lopey cam. I installed a quadrajet and got it adjusted properly, installed HEI, got the vacuum advance on the correct port, swapped in a torquey cam and some reworked heads, set the timing to 12*, and it runs much better than it did. Just seems to lack power on the grades, even with overdrive disengaged. It has been on many 1,000+ mile trips, though, and does so reliably.
