How do I calculate compression or guess

You indeed have my sympathies with the local ordinance; I am building a garage just to satisfy the same crappy issue. The golf course neighbor who sicked them on me and another gearhead nearby had better watch their step.... the next gang of drunk golfers who come onto our property may generate a call to the sheriff's office and a letter to the zoning board about the golf course being a public nuisance.

With the right range of numbers, you can get pretty close. Look up the Pat Kelly calculator (that I like) and use the 3rd tab.
- Nominal deck heights of an LA block are 9.599" or 9.600". Magnum block is 9.585". With these numbers and the compression height of your piston, a 6.123" rod length, and a 3.58" stroke for the 360, you can work out the deck height. For the pistons you mention, I compute a deck height of -.028".
- Nominal head combustion chamber volume for the 360 head: I'd use 72 or 74 cc for a ball park number.
- Nominal Felpro head gasket thickness is .051". Compute the volume from that and a 4.17" gasket hole diameter, or plug the number into the calculator.
- Piston eye brow volume is the 5 cc's listed for that piston.

For comparison for your results, I get 8.77 SCR from the above mentioned program, your pistons choice, 74 cc combustion chambers, and standard Felpro gaskets. That is a good compression ratio, but not a high one IMHO for a street engine.