IIs there a way to bleed the MC on the truck?
I'm curious about this too. Not least because between bench bleeding and fitting there is the possibility of air entering before the connections are made.
In theory the same as bench bleeding could be done in situ via the pedal with the brake pipes disconnected.
You need to bench-bleed, because there's a LOT of air to be removed. Once the majority of air is gone via the usual method, on-the-vehicle bleeding is recommended.
Leave the brake tube(s) CONNECTED. Most masters are installed with the front tipped "up" when the vehicle is level. Air rises--to the WRONG END of the master cylinder to bleed out.
Lift the rear of the vehicle so the front of the master cylinder is tipped "down". "Tickle" the brake pedal so that you apply the primary piston just a little bit.
OR
Unbolt the master from the firewall or booster, push the front of the master "down" by gently bending the tubes. "Tickle" the primary piston with a wood dowel or Philips screwdriver.
Either way, tap on the master with a brass hammer, or any other metal tool to encourage air bubbles to rise to the rear of the cylinder.
You should see air bubble into the reservoir as the piston is tickled. Continue until there's no more air bubbles. You are NOT pushing very far on that piston--1/4" or so should be enough. It may be that the primary piston area will bleed before the secondary.