For those with Magnums - What Mounts did you use?

What year and make car? Which size Magnum engine?
Since you said spool type mounts, I assume you are trying the Schumacher mounts. Since you said there is a gap, I assume you are installing a 5.2 Magnum engine. With all these assumptions, I will guess you are trying to install a 340/360 engine mount onto a 5.2/318 Magnum engine.
If this is the problem, order the correct 318 style mounts.