I suspect that the booster you have is a 7" single diaphram booster. Id so, a double diaphram booster will help. If there is room you can go to a 8" double diaphram booster, big difference.
There is also a difference in master cylinder bore between a F1 and the bigger trucks. You may have to change the master to match the wheel cylinders you have.
The metering block has to be a drum/drum metering block, not a drum/disc. With a dual circuit master cylinder you should use a metering block, it adds protection if one brake circuit fails.
The other thing to check is pedal ratio, you want a ratio of about 5 to one, or you will never be able to apply enough pressure with your foot to lock up the brakes.