Just to throw a couple of names into the hat- Eric was tight with George Harrison at the time so it is possible he could have contributed some guitar parts uncredited due to legal considerations.Also, Eric was part of Delaney and Bonnie Bramletts band around this time so he could have called upon one of their numerous guitar virtuosos to chime in.I read the Clapton biography "Survivor" several years ago but unfortunately cannot remember whether this point is addressed. I may just have a look in the loft and see if I can find the book.

Regards.

Sidewinder.