So you have a single plug 2001 16v engine, That want's to go into a 1997 shell?
Just check and see if the engine loom you got with the 16v engine uses the same connection to the interior loom as yours.
Ie behind the passenger headlight where they join.
If they are they same, it's simple plug and play.
If you changed the interior loom - its all the lights/speakers/rear screen/demister/all controls/clocks etc which basically is a full strip down. Not worth it..
Both are single plug - so chances are it will fit. However being a 2001 engine, that's around the crossover.. But my guess will be that the seller would of sold the cross over loom - then used a normal single plug loom.
