The P0300 is probably associated with the P1345
P0300 is just a random misfire, which could be caused by the truck being out of time, which is what the P1345 means (crank/cam sensor correlation, which controls your timing). Try reinstalling the distributor, and make sure everything lines up properly. Did you just turn your crank to 0 and set the new one "close" to where the old one was? These trucks are sensitive on the timing, the distributor needs to be set correctly, there are markings inside that need to line up when it is fully seated. If you pull the cap you will see two small numbers stamped on the inside rim of the casting, a 6 and an 8. The rotor tip should point to the 8 with the #1 at TDC on the ignition stroke. I spent 20 damn minutes getting mine right in the Yuke yesterday haha. Since your truck will run, you're obviously not 180 out. Best way to tell (without pulling your valve cover) where TDC is on 1 is to pull your cap and turn your crank to 0. If the rotor tip is close to your #1 wire, you're good, pull the dist and reset it. If it's close to #6, turn the crank one revolution back around to 0. If you're careful to pull the distributor up slowly and adjust it one tooth at a time, you can rotate the oil pump shaft with it, it may take a couple revolutions, but it's better than guessing where to turn the oil shaft to get it to align with #1.