All known examples of instantons on (non-trivial) asymptotically conical G2 manifolds asymptote to nearly K\"ahler instantons which live on the link of the cone. I will use this observation to develop a framework for studying the moduli space of such a G2 instanton, showing that the expected dimension of this space is the index of a twisted Dirac operator on a weighted Sobolev space. I will focus on the example of R7 where the link is the homogeneous space G2/SU(3) and show how one can use representation theoretic methods to calculate the expected dimension of the moduli space.