Help with pistons and rods

I am looking at purchasing these for an LA 360, Im running a Eddy 360 heads, not decking block or anything. Any idea of what compression itll make? Also these have rods on them and was set up for a magnum motor, will rods and pistons interchange on la to magnum?

Probe SRS 12351-030 piston.

http://www.summitracing.com/parts/pbp-12351-030