I have suggested him to change the radiator as it seems to me his car radiator is not in a good condition and obviously with the passage of time it life ends. So if it is not in a good condition, i recommend to replace it.
Fuel Tank must be replaced in case of an EFI engine, because a fuel pump is required which is already fitted in the tank i recommend. You can alter your current fuel tank as well but the appropriate way is to change it. However there is a place for this fuel pump on the top side of the tank under the rear seat. you can just cut it and put a fuel pump in it.
Well the Exhaust pipe is necessary to get the optimum performance out of this engine. Put exhaust pipe with 2inch dia.
Also do not forget you need the right ECU for the engine to run smooth. So look for an engine with complete harness and ECU.
With all this you will get max performance and economy of 13 to 14 km/l within the city.
If you want to go for an engine from civic 04 or 05, i think it will drop in without any alteration, but D15B Dual VTEC is the right choice if you find one with low millage.