65 Barracuda... Got BAD News...

Let's start with the basics.

A compression test is not "Pass / Fail" - unless you are selling a new engine to your wife.

A compression test will be a series of test pressures from each cylinder. If you have one cylinder that is 10% or more below the others, you may have a real problem - or simply a badly adjusted valve or carbon issue.

What were the compression test numbers? Remember that the 273 2v was a low compression engine to begin with. Post the test results.

If you bought the car recently, and have not driven it a lot I would adjust the valves, and do the seafoam treatment to get rid of some carbon. Drive it. Does it smoke? Burn oil?

As for swaps, almost any LA engine is possible, but the exhaust will be tough with the bigger engines. A 318 will work ok with the OEM 273 driver's side exhaust manifold.

B.