V8 swap? Or turbo slant six?

This is just my opinion but work on the safety things first before thinking about power. When I first got my Dart all the bushings were worn out, the brakes were crap, and my engine was definitely underpowered (a 273 with low compression in one cylinder).

I didn't care and drove it whenever I could. Anyways, one night I tried to put it in park on a sharply inclinded driveway and I missed and hit Reverse (it was dark). Car rolled back, I slammed on the brakes but they no worky. I hit a tree at 5 mph. I cracked the paint, scuffed some trim, and dented the tree. I drove like a grandma on my way home and on the last hill to get to my house, my brakes didn't work either and I had to take a turn at the bottom of the hill at 30 mph with 205/75/14 tires. Not a fun night...

Since then I fixed it up mildly, redoing the brakes and changing the shocks. I still wasn't happy with the stopping and handling performance so I scrapped all that. I'm almost done installing a Hotchkis TVS, 4 wheel disc brakes, and an 8 3/4 I built and know is reliable. All that has been done and the lowly 273 is still in there till I can find a viable replacement.

My point is, before you invest in fun, invest in safety. You don't need to go all out like I did.

And if I had to choose, I would have kept the slant six and slowly purchase the parts to turbo it. No need to build it up.