Need help perfecting the budget build hemi swap

The area/room for mounting the MSD box isn't too much of an issue. It's just finding a sanitary route to fish the harness into the cars cabin. Besides the unused air conditioning plumbing, there's an oval plastic plug through the firewall, below the steering column, that I think will do the job. I just need to find some sort of fume/water tight oval grommet to replace the plastic one currently there. I'll need to be creative.