Common sence says use methods of grafting you know..... as you have guesed we have no experience with your "problem" so please go ahead & try several methods then report back with the results. Sorry could not be of help but now you may be able to teach us

You might be able to graft a Persea borbonia to a P. palustris and vice versa, but neither would work on Magnolia virginiana because the Perseas are in the Laurel family (Lauraceae) and the Magnolia is in the Magnolia family (Magnoliaceae). While both families are ancient, they are quite distinctive both genetically and vascularly, and will not create viable grafts. This question is four years old, so the asker has probably already discerned this, but I thought I'd try to make it clear.

Here is a link that might be useful: Laurel family article on Wikipedia

Also, you may find the accompanying document link interesting. The limits of Persea compatibility seem to have been at least nominally set out.

Here is a link that might be useful: Graft Compatibility in the Genus Persea (1958)