Do I have to mount the ignition coil close to the distributor? Or can I hide it farther away...

 

Back in the day I've mounted some of my high output coils on the firewall and even one on the inner fender. Had to have a longer coil wire though. I don't think the placement of the coil is an issue as long as you have enough wire.

 

I've got mine mounted on the firewall with no issues

 

I have seen many installed under the dash and the wire run through the firewall.

 

I have a high energy MSD unit mounted on the back portion of the intake on my 351W. Used a 1/2 thick aluminum plate and bonded it to the manifold after machining the mounting holes. Shock/heat isolated, out of view, and relatively close to the distributor.