I can address your first question from experiance. You won't be able to slide a 3" narrowed beam back in your car with out some kind of clearance.
I narrowed a beam on my Ghia 2". (1" each side) I didn't notch my inner fenders, just some gentle persuasion with a 15lb sledge.
People talk about notching the inner fender work because when you narrow a front beam the shock tower hits the inner fender.
Just to give you a visual of what I'm talking about, if your car still has the beam in it. Jack the car up, crawl under it and measure the shortest distance from the shock tower to the inner fender. If it's less than 1.5", you'll run into that much interferance when you narrow the beam, plus you'll want clearance so the body isn't resting right next to the beam.
As for the second question, I have little to no experiance with that. Good luck.
