elev8_dude:
The neatness or simplicity of the installation would be down to the wires going to the fuse box, that sounds almost too obvious. But what I mean is that the watson main fuse panel really only saves you the spaghetti of the wires from the fuses to the replays and gives an idiot like approach to connection.
When the kit is going in afresh all the connecting wires are going to be the right length and routed accordingly. When you are retro fitting it will certainly require extending some wires and the untidiness comes back. Maybe that is too much of a pure view of the problem.
As far as connecting all your items up it wouldn't be an issue, there are 3 spare fuse locations and the MSD would be run off a relay anyway. The kit expects all gauges to be run from a single fuse so that would be straight forward.
Although rereading you post, why not just change the just the fuse panel and relay with something like this.
http://www.vehicle-wiring-products.c...hotos/lfb1.jpg
Or go one step further
http://www.vehicle-wiring-products.c...o/1520demo.jpg