Are the motor rebuilder and the resto shop are two different guys or did the resto shop rebuild the motor ?
If the motor guy handed you the motor and it sat in the resto shop ( of a different owner than the motor shop ) for two years, I would not blame the motor guy for sticking to his one year guarantee. If they are one in the same, the resto guy knows you did not drive the truck..
If the resto guy recommended the motor guy, you may be able to lean on somebody. If you picked the motor guy yourself, you are on your own..