SSeater, the shifter position is not a problem. The most 'rearward' position on a Magnum is actually a bit too far forward for F-bodies, but nearly perfect for Fox & SN cars. If you ask your buddy, I'm sure he'll tell you that he either used some sort of offset shifter or had to trim the opening in the floor to accomodate.
You are however, going to have a problem getting the trans into your car unless you're using LS power. The LS Magnums use a different 'mid-plate' on the front of the trans, which doesn't offer provisions for your factory cable clutch release. Additionally, the LS input shaft is longer with a smaller diameter pilot.
You could likely swap the mid-plate and input to make it work, however beware the trans that has been subjected to such abuse! Losing a cluster is about as bad as it gets in the world of transmission failures. Personally I'd have a hard time believing that a layshaft could go without doing a great deal of secondary damage--or maybe the cluster was the secondary damage? I could get really long winded with this, but to sum it up, just imagine all the carnage that takes place once pieces of hardened gears start flying around inside a gearbox--yikes!
Anyways, I hope that helps SSeater. For what it's worth I put a Magnum in my '94 GT with help from D&D and absolutely love it. No serious drag use yet, but on the street it's by far the best trans I've ever rowed gears with. Good luck!