My read is that he wants a single chainring w/ a rear derailleur and multicog freewheel. I would just keep both chainrings and the front derailleur, because I like gears, but if you really have your heart set on a single ring up front, just use the inner of the two current positions for best chainline.
If it's a PX-10, it is not a Carbolite frame, but something far nicer. What decals, labels, etc. do you find on it?
You do not need to change the fork just to change the brakes, and there is probably nothing wrong w/ the brakes you have that new KoolStop pads won't fix.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069