I'd always do that - if it was. However, I was unable to find any P3D release for either the C-130 or 707. It would be very nice if there was one but if there isn't, developers should be happy to still earn money for something they didn't spend time for (making a product officially compatible with P3D). Of course, that's totally out of support but unless it's expressly forbidden to install into a successor product of the sim (as is with PMDG's products), it's not wrong unless you start patching or reverse engineering the original files. If just installing to a different sim and checking if everything works would be illegal, that tool I was speaking of should have been banned a long time ago.
Anyway, good to know it's forbidden to discuss compatibility issues in this forum. I will keep out of this forum unless it's for support questions to developers who (unfortunately) put their official support forums in here.