Stick with 2.5 inch exhaust with nice muffler. And please don't worry about the gas mileage because it will never be pretty but then again you already knew that and decided to go for 1jz.
Use this car as a weekend car or for car meets.
Rare-end in your car will crappy with that engine, you shouldn't have any problems in finding
Toyota
highlux, land cruiser or even a
Toyota
jeep. Be prepare to change pumpkin gears because ratio would make the car drive like a
Gudha gari
..
Good Luck