I personally wouldn't run both the old halogens and the LEDs at the same time, lest you be accused of being "rice", but that would certainly be unique
But yes, if you have the Mk7 with halogen tails currently, you can swap them for the Mk7.5 dynamic set with the use of a harness.
And another vote for
@ZERO815 , he is an amazing resource. His harnesses are not the cheapest, but without question provides the most comprehensive support of any of the harness suppliers (a lot of whom just sell to you and you have to figure everything out yourself).