They were intended to be direct replacements for the Sea Eagle AShM and were to be fitted on the No.6 Squadron "Dragon" Jaguar-IMs with the LITENING II pod.
Also, I agree with whiplash that the most likely candidate for a LR SSM is the Kh-37 particularly since it will have both INS/GPS mid-course guidance, and is rumoured to have some (even though 'opaque) compatibility with the Kh-35, which India has already acquired.
The DARIN-III upgrade makes it possible. Until somebody posts the exact specifics of the upgrade, I won't be able to 'prove' it to you with what's available online.
But, 68 of the IAF's Jaguars have either undergone or are undergoing DARIN-III, out of 120 that are also being equipped with a new engine.
In any case, Boeing responded with a proposal for the Harpoon for IAF's Long-Range ASM tender, so unless something is amiss, it can or will be able to, carry it.