AFAIK a backing plate may do it, but are you sure this is not already sealed?
I agree, 10.5:1 is above the normal safe choices for turbo, but if max boost is mild (10 psi?) and you don't mind a lot of T&T to get the advance, vacuum advance/retard, knock sensor, and anti-det injection adjustments good it could work. The safe settings must kick in just before you get to low vacuum (even before boost) with that static CR.
The usual warning: 1 mistake + 10 seconds of full throttle = drive over the crank.
Re: Magnum cam. This is 268° nominal, 218° @ .050", 110° LSA. The range is OK but IMHO that's too much overlap.
