Ok...

What you need is the Manual brake firewall plate for your body style and year - got one at Moparfest last year for $20 from the guys from Quebec. They had a bunch.

Your iron 4-bolt m/c will bolt up to this plate but if you switch to an aluminum m/c then you need the adapter.

You can jimmy your "power" plate to work. Cut a piece of metal to fill the big hole and weld it in place. Line your m/c's bottom holes up with the bottom holes in the plate and drill two holes to match the m/c's top holes. Measure and bore a hole big enough for the m/c's flange to fit through.

You should also try to find the rubber boot that seals the back of the m/c.

The brake rod is sold separately - try Mancini's for either the standard or adjustable. Or find one off any Mope and make your own adjustable.