You will see a power gain due to increased compression. How much will depend on everything else in the combo. In any case, the added torque and HP will be noticable.
Magnum heads are a bolt on with the proper parts. Things you will need are; head bolts, valve covers, oil through lifters (AMC style), oil through pushrods of the proper length. You can have the heads redrilled to accept the LA intake. I will assume that the heads you get have the 1.6 rockers already.
Things to watch for are; the size of your cam. If it has any more than .525 lift using the 1.6 rockers you could have a real problem with retainer clearance. The stock springs may be a little weak if you have more than .475 total lift.
I run 10.58 to 1 compression and a Comp Cams Magnum 280H and have no detonation using mid-grade gas in my LA/Magnum 360. I also have 400+ HP.

Jack