I'm not aware of a kit, probably have a custom aliminum one made by BeCool or Griffen or someone like that. There's another name I can't think of that many have been using. If you have someone that can weld aluminum you could get one for a '68 and have them relocate the necks.
If you do a Google search, there are several companies offering exactly what you’re looking for. Now, there expensive as hell, but I suspect it won’t be the first time you run into that, doing a Coyote swap.
The Coyote has the same coolant outlet locations as my 3.7L(passenger upper, driver lower). I used a SN95 aftermarket aluminum radiator after cutting open my radiator support:
If I had to do it again, I would instead choose an aftermarket '66 Thunderbird aluminum radiator, it would tuck under the support just a little bit better than this one does and its also an expansion tank design.