Main bulkhead bolt => Blower Motor => Dashboard Bolt => Body Panels. (With branches elsewhere along the way).
They will have little/nothing to do with your sucky reception if WRT being "weak"...more for interference from other sources, "static" and/or electromagnetic interference.
Maybe TMI, but without the grounds, if you were to drive under low electricity transmission lines, your radio would cut out (some do anyways) and your engine may die (screws up the electronics...).