gain, bandwidth and GBWP of current to voltage converter with op-amp
The GBWP for the setup stays  constant. This means reducing low frequency open loop amplification by negative feedback increases the bandwidth by a same factor (assuming your open loop setup has a single pole, meaning gain rate of closure of 6dB/octave).
Beware of proper uniting, you can't just divide bandwidth by resistance value and still have bandwidth. 

To calculate closed loop gain you will need both resistance values, as you stated yourself. Suppose the open loop gain is 10^6, then there will be a pole at 10Hz (GBWP = 10 Hz * 10^6 = 10 Mhz). Reducing gain to for instance 100 shifts the pole to 100 kHz. (100 kHz * 100 = 10 MHz).

In your current to voltage transactor, it looks like there is only one resistor. There is one other, however, the output impedance of your input source. Both resistors determine voltage amplification (A = - Rsource / R). So in effect, bandwidth depends on your input source.

Also note that gain bandwidth product requires the notion of unity gain. And how exactly do you define unity gain of a current to voltage transactor?