You won't have to move your pedal adjustments, you can just crimp the cable at a different length. This will make more sense when you do it.

I honestly think that modifying the firewall etc. won't be worth all the effort. That will be quite a bit of work but to each his own. Just remember that on the other side of the firewall there isn't much room for engine components depending what you are sticking up front so you may want to leave the final placement of your pedals until you hang your engine.

I would also hesitate to cut the back of the rudder mounting "feet" and extend it on the front. The rudder pedal force will now be trying to pull off the thin birch floor boards where as before you had a wide foot print pushing against it. You could get around this by custom making a large washer plate that goes on the backside of the birch.

Just my $0.02