which year engine will fit a 96?

i have coolent in my oil.i was told that it is the head gaskets.may have all ready hurt the engine although it sounds alright.when i first noticed my coolent had gone down i filled it up drove about 20 miles total the next day and noticed it went down again.filled it up ran the car to check for leaks ,none ,checked the dip stick full ,thick and milky.its been parke3d since while i try to locate an engine for it.no luck , a 3.1 for that yaer seems to be hard to find around here.i have found one from a 98 century and would like to know if it will fit in without making any changes.if not ,which years will or from what other cars?

Try this web site: car-part.com. You can search wrecking yards all over the US and Canada. Practically any of the 3.1's will fit your car so you should be able to find one fairly easily. Take one word of advise though if it is a used one change out the Lower intake manifold gaskets before you put it in the car. Much easier to do and a lot cheaper too.