i'd take a guess that this truck has a UA or UV mazda engine
he did say it was an "LP mazda engine"

The fact that it will start and run after it gets warm gives me the impression that this could be a fuel problem.
It sounds like the vaporizer might be clogged up, possibly the mixer diaphragm, or even a faulty fuel lock valve.

Does this truck by chance have a vacuum operated fuel lock-off filter on it? It would look similar to the vaporizer and have a vacuum line running from it to the base of the carb/mixer.
This component may be clogged up or have a vac leak in the line, this would hinder it opening up correctly causing the hard start condition.

Also what about performance, does it have any power problem symptoms like low power now? stumbling or just won't pull well under a load?