Not sure what you mean by 9 LEDs in parallel being "enough". Enough for what?
As for 32 LEDs in parallel, I can't imagine any subway car holding that many LEDs! If you have 32 LEDs each drawing 20mA @ 3.2V, that's a whopping 0.64 Amps of current. A 20 ohm resistor would drop 12.8 Volts but in doing so would become quite the heater; Power = Volts x Current = 12.8 V x 0.64 Amps = 8.2 Watts. You'd need, say, a 10 Watt resistor which would probably melt something in the car. That's a lot of wasted heat considering that the LEDs themselves would only be consuming 3.2V x 0.64 Amps = 2 Watts. When a circuit draws this much current, you would use other techniques (instead of a resistor) to control the current/voltage into the array of LEDs.
If by removing bulbs you mean to somehow insert 3 3mm LEDs (plus resistor) in each location where there's presently a bulb, then OK. You'll have to experiment a bit since the 3mm LEDs you mentioned have relatively narrow beams (about 30 degree) while an bulb projects in all directions. If you search the forums for LED passenger car lighting you'll see dozens of threads on the virtues of so-called LED strip lights which run at about 10-12VDC. These are nice because they have wide-angle projection for more uniform illumination
I cut the track using a metal-blade bandsaw. As mentioned earlier I tried to cut just the outer-rail with a hand hack-saw but couldn't get the right angle or orientation...so ended up slicing the trackbed itself to get to the rail.
