273 time to 'fish or cut bait'...

Sounds like you have the major parts to make two cars.
You should focus on one, sounds like the four speed car is the better candidate.
I would buy a cam that someone else has had a good experience with. See ToolManMikes 273 build. The part numbers on the heads and intake would help a lot.
I'm not clear on your goals. An early Barracuda can be a really nice quick fun car that can be driven comfortably at freeway speeds. But if you are looking forward to also beating a 2017 Corvette in a race ( any race) that's a BIG task.
Hope this helps.