differences between IF Transfor. in the SC schematic?

Hello, I want to start building the SC modified (http://thereminworld.com/article/14272/silicon-chip-theremin-modifications).

After doing some research i found that both IFT 42IF203 and 42IF202 are apparently obsolete or non-stocked. Are there some substitute for those components? I found that the 42IF102-RC and 42IF103-RC are very similar, but as I have never used an IFT before so I could really use some advice.

Here are the schematics of both IFT versions:

http://postimg.org/image/t5apva8m1/

The 42IF102-RC (white, 3pcs needed) and the 42IF103-RC (black, 1pc needed) will work well in the SC.

Some question, does is possible to replace these variable coils with coils-variable capacitor?

it depends from the circuit. In the SC theremin, the pitch antenna is directly in parallel with the tank circuit. Varying the capacitance would also mean not only the resonant frequency but also the pitch range which is not a good idea. out of that, it's a Hartley oscillator which needs a tapped inductance which you can only find in these small IF transformers.