Boy, my experience with the 305 is sure different from all youse guys. I have one in an '84 K10 with over 200K miles on it. The axle ratios are 2.73(not 3.73) so it's geared very tall. Granted, it's no jack rabbit off the line, but it will still run circles around my '37 1/2 ton with a 235 and 3.38 axle ratio. It's a much heavier truck than the '37 also. The gas mileage is not great though(around 14mpg), probably no better than a 350. I think it would make a pretty good motor for an early 1.5 ton, especially if you are keeping the original low gearing. The 305 will happily tolerate many more rpm's than an early 4 main bearing six giving you better road speed. The low gearing of the truck means you don't need a lot of low end grunt. If you already have the 305, I would say go for it. Myself, if I were going to do this project, I would opt for a 350 though. Same amount of work to install it, quite a bit better power, and probably the same gas mileage.
