In your case it only makes sense to install a V8. Normally I would never recommend this swap to people with newer 1997+ cars, but the older V6 in the 80's cars are quite low on power and it would take far more money to make the V6 stronger than installing a V8.
If I were you, I'd be looking for a 351W and transmission. You will eventually need to upgrade the rear end, but as long as you used some common sense you'd be OK for the short term. Also, look for a wrecked GT around the same year as your car as I would dare say you could find a complete car with every part you need to do the conversion for under $1000. You should also consider swapping in the drivetrain from an 80's T-Bird Turbo Coupe or even a newer supercharged Super Coupe. You would only be limited by your resources as to which way to go since using a carbed V8 would most likely be the cheapest and easiest route.
Again, I would not normally advise a swap like this but it is the only logical way to go if you want performance.
1988 Mustang LX coupe too much done to list........