Hello. New to the forum and grand marquis ownership. I have a question. I have a blown engine in a 97 grand marquis gs and a smashed 99 with 500 miles. I would like to put the two togther. I was wonderning what i will need to change over? Is the harness the same. Do i need to change the manifold. I have the new tranny too and will most likely change that out because the 97 has over a hundred thousand . Is there any one that knows this please post or pm. Thank you and I will happily enjoy my big car in the era of the tiny one.

 

I'm not sure about the harnesses, but you could swap out the engines and just reconnect everything electrically and swap the engine control computers and it should work. I think there's a few bolt pattern changes for the heads and intake (if I remember correctly) from 97 to 98, but the rest I think is the same. If I'm mistaken, someone else will be along to correct me.