I'm building up an old Centurion Dave Scott Expert frame (1987) for my oldest kid. My apologies to the purists, but I'm going with brifters. I have basically all the 9 speed stuff I need except that my right side DA shifter is broken (typical problem of a worn internal plate and no upshifting unless the outer lever is held in position). I also have in stock a 105 10 speed left STI lever and a cassette. I'm tempted to find the drivetrain parts I need to just go 10 speed.

So, my options seem to be to either repair or replace the DA9 right shifter or go 10 speed drivetrain. Looking for opinions/suggestions.

As far as i know, I need a right 105 STI shifter, 10 speed chainrings, and a 10 speed chain. I believe I can use the old Ultegra 6500 cranks and derailleurs, and I don't much car about it looking Fredish. My only concern is whether the 10 speed chainrings will work properly with a 6500 crank.

I'm tempted to rebuild the 7700 shifter, but finding the replacment part is a problem. I could buy a used one on ebay i suppose, but even these are going for $70+ and then there's no guarantees.