I would emphasize removing the water pump, check out the opti as steveo mentioned. If you have a delco-remy distributor base (the aluminum casting) a drop-in replacement pickup can usually be had for a reasonable price from a vendor on Amazon called AIP Electronics. I would probably advise against leaving an original Mitsubishi sensor in if you have no way to know how old it is and if it has the Mistu logo on it, it will likely be 15+ years old.

More importantly, if you don't know the engine's history I'd replace the water pump so you know it won't spring a leak in six days / weeks / months and ruin the opti. Also, replace both oil seals in the timing cover. The water pump driveshaft seal does need a specialty tool, but one can be improvised with the case of a sharpie or a piece of soft copper can be flared to create one. This seal is terrible about letting go early and spewing oil all over the front of the engine and rear of the opti.