Some pumps run in only one direction, and this could be true about this pump. If you mount it face to face with a coupler, the engine will run in a clockwise direction. The pump you want should run in a counter clockwise direction. Have you figured out the HP required to run this pump?
If the pumps specs are 13 GPM @2000 psi, the pump will need about 18 HP.
If the pump specs are 13 GPM @ 1000, the pump needs about 9 HP.
If the pump specs are 5 GPM @ 1000, the pump needs 3 HP
This pump is only $125. and new. I think I would go for the new pump rather than pay for an old pump with questions.