Maybe if the truck were higher geared, maybe. But then you couldn't work it as a truck. An overdrive tranny with the I6 would be the way to go. I'd bet at comparable rpms the difference in gas mileage between a 305 and a 261 would be negligible. And probably better with a 235. And as Joe pointed out, 305s are just not designed for big truck use. I had 2 cars with 305s. A 79 sunbird and an 84 trans am. They were both little and lightweight and I was still underwhelmed by the engine performance in both of them. The sunbird was kind of a sleeper for a high school car though, everyone thought it had a 4 banger as most of them did.
