For a no-sew/no-cut option, I think this mod works pretty well...here's the link on the now-defunct Kifaru Forums:
As you can see, you'll have to scare up some hardware, but you can get the Marauder to ride pretty well with the HPG harness--the only issue might be if you need to pack to ride high for some reason...the extra hardware adds a few inches to the minimum strap adjustment length.
FWIW, I ran a G1 Marauder/HPG harness combo as my EDC and was quite pleased with how it carried. I'm thinking of doing the same mod to the minty Marauder I just picked up, but I should mention that you'll probably have to remove the thumb-loops/tabbing loops off the original Kifaru lower shoulder straps to get them through the ladder-lock buckles of the HPG harness.
To be honest, though, if I were you, I'd probably leverage your Kifaru pod; i.e. just throw your Tara w/ harness in it and have it accessible and ready to go without a lot of faffing about...you're not talking about a real weight penalty for the second harness, especially if you're rolling with old-school Kifaru gear. ;)