propane won't make your truck go faster than gasoline(if you're comparing 2 identical engines, one running gas, one running pane), since it has less energy potential than gasoline. however, it is very high octane so you can crank the compression up or run forced induction without pinging, which will translate into a lot more power.
the main benefit of propane is that you won't stall on angles like a carb, but doesn't require a complicated EFI swap. most kits just use the throttle plate from your carb and mount a mixer assembly on top.
it's also much cleaner burning that gasoline, so clean that when you go to change your oil, it will still look nearly brand new.
Well on got propanes website they claim that thier kit is a big improvement if converting from carb but from EFI I am pretty sure there is a small loss, but they also sell a turbo kit
