Is the McCrae version of "Doin it" prior to Chuck Strong's version ? It seems to be the case according to that review : https://www.rushhour.nl/record/vinyl/private-wax-super-rare-boogie-and-disco. That would be logical as Willie Hutch also wrote "Keep the fire burning" for the diva on the same LP. Plus I read an interview of Gwen McCrae on the Soul Survivor mag on which she somewhat states that Willie Hutch wrote the song for her during the "On My Way" recording sessions, and she doesn't even mention the Chuck Strong's version.