I think from memory that the 8753D has its own test set installed as default, so I assume if it's the 75 ohm option it will have two 75 ohm N ports. You can use two minimum loss pads, but of course you will lose more sensitivity and therefore dynamic range, each pad is an additional 5.7dB loss.
Always calibrate at the point where you plug in the DUT, so that will be a 50 ohm cal. This means you're only measuring the DUT, not the cables or indeed the minimum loss pads.