Here's your first problem:
The mustangs are going to outbeat your car. Problem is you don't have the gears to do any sort of mustang hunting. If your running that low of a gear, numerically mind you, then you are much better of going with the TH350. I will bet you 50$ that if you put that 2004r in your car with that gear selection in the back, you'll never use the 4th gear and barely get any use out of the 3rd gear...
I learned real quick that building a bada** engine is nice, but if you don't address the overall combination of your drivetrain, your gonna be suckin to the 4 bangers. Now why are you gonna let some stupid mustangs get to you? There are dozens of those cars out there and I've seen every single variation of them. They can wreck their cars and go out the next day and buy one identical to it. YOU CAN'T DO THAT WITH YOUR CUTLASS! I'm 19 years old and trust me, I know what it's like to want to smoke the living hell out of everything in the parking lot and on the street. Soon you learn that you gain a whole new respect for you car once you start building and taking car of it.