I have a 91 350 TPI. Added the K&N oil breather to the passenger side and still running the CCV on that side. and want add one to the driver side aswell. My plan is to keep the pcv valve in location on the driver side and drill an additional hole in the driver side valve cover towards the back to accept another breather to look uniform. Is something like this possible to do? Or will it damage my motor?

That's where I stand now. I want to put the pcv valve back in its home and re route the filter on the drivers side to the back of the valve cover.

I don't think it would damage the engine mechanically but the PCV system might not be as efficient. It'll have a tendency to suck blow by fumes from just the driver's side breather rather than from the entire crankcase.

Inefficient or non-existent crankcase ventilation can result in excessive sludge build up.