Quoting from the XD-V75 manual:

"...To set the THH12 or TBP12 transmitters into the RF1 mode, enter Setup mode to display the current channel, then while holding down the SELECT button, press and release the ON/MUTE button on the THH12, or VALUE button on the TBP12. The display will briefly show [XD-V75 RF1] or [XD-V75RF2] to indicate whether operating in the old or new mode, respectively. This setting is retained when powering off, so, as a reminder, the display will also show this indication [RF1 or RF2] each time power is turned on..."

I'm confident that you'll have no problems.

The "icing on the cake" would be if you could find a friend (or "sweet talk" a Line 6 retailer) who not only has an XD-V75 receiver, but would also allow you some time online with it (and your V70) to effect a "75" firmware upgrade via USB and Line 6 Monkey.

That would effectively transform your receiver into a V75 and give you a whole bunch of really useful new "toys".