Sell it, and buy one with the engine in it that you want.
Seriously, sit down and do the math.
Lets say you get an LS1 engine, at the low low price of around 5,000-6000. Then you figure installation costs, which will be another 2-3,0000.
So, you're at $7000, for a stock LS1 engine, when you could buy a 2000 Trans Am, with that engine, for around 7,000 to start with. And not have to worry that it was installed properly.