how much boost can u run on a stock 2g 4g63 motor swapped out of an eclipse into an avenger, and can u use the stock f5mc1 tranny that came in the avenger with the 420a with a racing clutch installed as well as a short throw shifter????

 

The two motors are different, so you can't use the 420a tranny on a 4g63 or vice versa.
I think you mean...how much CHP can the 4g63 make? PSI is irrelevant in any motor. It's the motor's capability that's relevant.
The 4g63 uses an iron block and forged internals. The 6 bolt motor is rumored to be capable of 400-500chp where the 7 bolt motor was rumored to be less, 400-450chp. I personally wouldn't try higher than 400chp before building my motor because either one is know to be capable of that, so those rumors mean nothing to me, but that's just me.
The 420a in stock form is capable of ~300chp. Then again, it doesn't have forged internals from the factory but you can put in aftermarket forged internals.