in the second gen cars it is extremely expensive to swap in a 4g63 because so much has to be changed out its just plan cheaper to buy a turbo car to start with. The 420a motor is a good little motor it only has 1 major problem and thats that one or 2 of the head bolts bottom out in the holes and don't apply proper torque so the car blows head gaskets. The 420a in the eclipse has a different head then the rest of the 420a motors but the bottom end is the same so buy the thing ,go get a motor out of just about any dodge neon,stratus,intrepid,minivan and swap your stock head on and your good to go
Or you can go find a 2.4 motor swap in srt4 pistons and rods swap on your stock head and do a custom turbo kit