As many of you have found they no longer make the radiator reserve for the 02-04 1800s. This part breaks and that shit sucks. I ordered one from a 1300 part number 19101-MEA-670.

They are extremely close in shape and have the hose fittings in the same places. You will need to fashion a small bracket as the mounting brackets don't line up. I ended up not using the top bracket in the picture as it fits in there so snugly there's no way it will come off with just the one bolt.

I did have to take a Dremel to the fitting of the large hose that connects to the fill cap as the replacement was too big and kept splitting the hose.

I found it easier to buy a 6 foot length of half inch radiator hose from AutoZone and Fed that from where the fill cap is under the left side cover to where it attaches to the reserve tank. I attached it to the reserve tank and clamped it down before bolting the tank to the bracket. Then you can pull in the slack on the hose from the top while you get the tank in place. Cut the hose at the top, reattach the fill spout and you're good to go.

It is an extremely tight fit I will say that. You gotta manhandle it in there, but I am pretty confident it won't go anywhere.