I've been using the F-250 C/S m/c with the cheby conversion since before the turn of the century, and I like it. I figure to add some insight here.
The stock size m/c (1.000" bore) will give you the most stopping power. It will feel soft, but that is because it gives the greatest leverage advantage, the most power for effort put in to it by your leg. The down side of it is that it requires longer travel to get this power. My pedal was coming to a stop too close to the floor for me to be comfortable with it. If a problem/leak were to occur later on, I wouldn't be able to press the pedal further to get some extra braking pressure.
Larger bore m/cs give a firmer feel and ergo a shorter throw of the pedal, but require more muscle to achieve the same stopping power.
A big mistake many guys make is assuming firm brakes are better brakes. This is a totaly different issue than the softness caused by air in the lines.
The size of the m/c is just a variable in a leverage system. Using a larger m/c gives the exact same results as shortening your brake pedal, less distance and more effort. It boils down to "preferance." There is no better or best, or worst.
The '76 F-250 Camper Special came with at least 3 different bore m/cs. Mine has a 1-1/16" bore. Others have 1-1/8" and 1-1/4" bores. I think the 1-1/8" is most common. Most people who have tried the 1-1/4" m/c will say it requires too much muscle to stop safely, unless you're using a power booster.
And that is a different subject.
