I'm not sure what the used car/parts/repair labor markets are like in Tijuana, but in the USA, that swap would make no sense. You can more than likely buy a complete SRT8 for the cost of the upgrades you're suggesting, if you're paying market labor rates. Worse, when you're done, you still wouldn't have an SRT8, you'd have a base 300, with tiny, inadequate BR3 brakes and mushy base 300 suspension, with a big engine.
If you add in the cost of things like SRT8 brakes and suspension (the correct front knuckles alone are hard to find and very expensive) you'd be looking at even more money. And when you're done, you'd still have a plain-Jane base interior and body.