Hi,
The input bandwidth of the DAC is limited by the FIR1 (2x interpolator) low pass filter limit. To generate 75MHz, you will need data rate higher than 100MSPS. I suggest that you use 200MSPS input rate and 4x interpolation to allow enough input bandwidth for the 75MHz.
See section 4 of the following app note for detail:
http://www.ti.com/lit/an/slaa523a/slaa523a.pdf
-Kang