V8 swap? Or turbo slant six?

well this question all depends on how much money you have.

if your really on a budget like most of us then why not drive the car as is and get to know it first. Then down the road maybe a super six set up (they don't cost all that much)

Then even farther down the road maybe a small block swap. A 318/360 can be done very cheap.

You would be surprised what a well tuned slant six can do. There is a good reason Chrysler put them in 100s of thousands of vehicles over the course of 25+ years.