are these fuel pumps interchangeable?

1998 is a return system. 1999+ is a return-less fuel system.

In a word, no.

A pump from a return-less car has a fuel pump driver module that controls pressure by rapidly turning power on/off.

A return style system uses a regulator to bypass excessive fuel back to the tank. The pump runs all of the time.

Putting a return-less pump in a return system (assuming it fits) would have the pump running 100% of the time. The pump is not designed to run at a 100% duty cycle and would have a short service life.

There is a difference between the V6 and V8 fuel pumps. The tanks are the same.

Regardless, recommend for a 1998, that you stick with a 1996-1998 donor car. Much better chance the electrical and mechanical will fit/work.

Before buying a salvage yard fuel pump, check prices on new. A couple of points. It's a lot of work to drop the tank. As well as the pump from a car that old may not be much better than what you have. At least, check the $$ before hand.

Try this. Go to car-part.com. Enter your make, model, year. Search for the needed part. Made note of the other cars that come up. This will give an idea about the interchange.

Also go to oreillyauto.com. Search for the part. One the compatibility tab, there is a list of other cars a particular part will interchange with. This will also give a great idea of what will work.

OBTW, do you homework before dropping the tank. Remember to get a new tank grommet. It is important to cut the old grommet completely away before dropping the tank. Damage to the filler neck is likely and for that MY, replacement filler necks can be hard to come by.

Good luck.