What year is the motor? Is it the blue colored two-stage (two impeller) lower jet unit? How much is the seller asking?
Personally I would stay away from any jet lower unit other than the Speciality Manufacturing model. These SM units are simple, time tested, bullet-proof pumps that are very common and therefore have excellent parts availability. If you're still interested I would suggest you make a very low-ball offer based on the obsolete lower unit. Good Luck.