1967 Dodge Dart Post

If it's a 6 it has a 7 1/4 rear axle, and if you put much power into that it will die. So you need something bigger. Options depend on price. I am biased. I want a 3rd member rear so I can easily change ratios, but the 8 3/4 is somewhat expensive, and it has no stock easy route to big bolt pattern. "Or cheap." You can go 8 1/4 for a mild build and you can find them--factory--in big pattern.

You can go "cheap" on rear springs. I junked a car, used all the longest leafs out of both spring packs to form 2 new springs with 1 or 2 more leafs than stock. Lucked out, they worked great

You can stay with small pattern but limited on wheel choice. You CAN however find some custom wheels in the small pattern. Me? I would go big.

Suspension. Too many options to name. If you are low budget, you can upgrade with newer stock parts. One "big thing' is that your present K has the dreaded "67 only" idler arm. Since you want to go V8 it would make sense to find a V8 K, 68 or later or 73 or later

AFTER you make the decision on the K, I would get "at least" a factory anti -roll bar and look for larger torsion bars, then rebuild the front end and new shocks and decent tires. You will be amazed how much better the handling becomes