Picked up the Barracuda! Love my first early-A :)

The 273 intake port is smaller than the 360 head port. While not ideal, this mismatch is far better than a large port intake and a small port head, which would create a "step" in the path of gas flow. I doubt that somebody would put small port heads on a 360, it would be a step backwards performance wise. Being a 66, the factory intake would bolt directly onto 360 heads (64-65 would not) You would have to remove a valve cover and read the casting number to confirm which heads you have.

Assuming you have 360 heads, there is a detrimental exhaust port mismatch. The original 273 manifolds are quiet, fit great and flow so-so at best. Their port opening is notably smaller than the port on the the cylinder head. This means the exhaust gasses encounter a "step". Such a mismatch can be easily blended away by gasket matching, solving part of the problem. But no matter what, their small runners are restrictive and they will only support 300 hp on a good day.

Will the apparent combo you have now work? Yes, and it will move a little Barracuda around pretty good. What is your major impediment to increased performance? The exhaust system. Can you put a really nice exhaust system under an early A-body? Yes. Cheaply? well, not so much.

You have a nice car, drive it and enjoy it. Should you become bit by the modification bug, we'll all be here to help you spend your cash.