To install Sparco seats in a 2003 ES, what would I need to buy besides the actual seats?
The side mounts? Flat seat base? Track set?

 

Mounting bracket and the sliders...

 

SLVROZ_03 is correct. Contact Sparco or a Sparco dealer and get the Lancer parts and you're good.

 

how easy or hard are they to install?

 

4 screws for the stock bracket to the Chassis of the car, then 4 screws underneath the seat cushion

 

Hardest one is the one underneath the center console! If not removing the entire console, make sure not to lose the bolt under there!!!

 

installing seats is easy... the four bolts that hold the seats in are easy to get to, tearing out the center console isn't that bad, either. you don't need to remove the entire thing--just the glove compartment-ish piece.

after that just get a 14mm socket on the bolts and you can pull the seats right out of the car.

 

whats a good place for after market seats?

 

Rallysportdirect.com or soloracer.com.

 

Soloracer FTW.