The car was all original, but I wanted something more fun to drive, so I am installing 4 wheel disc brakes, 5-speed close ratio trans, stiff springs and bar, Bilstein shocks, etc. I am keeping and restoring all the original parts so it can be converted back to stock is a later owner really wants to do it. I built a couple of Carrera Panamericana cars to this spec years ago, and they were a blast to drive.
Obviously you know what you are doing. For some this will always be Alfa heresy but, back in the Portello days, there were all manner of tuned Alfas being run by Italian Alfa guys, factory and otherwise. What you are planning is thoroughly doable, I think, and promises to be tremendous fun. My friend Bob built two similar cars: a Sprint Coupe and a Spider. Both were much modified (full-tilt 2 liters which still had enough oem1300 hardware to look like stock Veloches) but still looked oem stock . . . unless you really knew what you were looking at. We took the Sprint Coupe on a Hill Country tour and the ride was electrifying. With your engine and those close-ratio gears you are going to have quite a ride. By all means keep us posted.