I would recommend asking both old profs and any current boss or reading club chair or whatever. It would probably look best if you ask people who not only know academic performance, but also know the applicant's recent activities and qualities. It can never hurt to ask, so don't be afraid, but also don't be surprised if the prof does not feel comfortable writing a strongly positive letter for some one they have not seen in many years,
It is also good to note that many profs do not always remember people 10 years out. Many of my undergrad classes were so big that my profs would not recognize me on campus, so I understand what odds you might be up against.
The MCAT score is good, so I wouldn't recommend waiting too long because you don't want to let it expire, but it is always possible to wait another year if whoever this person is that you are posting for is not fully prepared to apply. Not having clinical is bad. You shouldn't spend thousands of dollars (and many hours /hopes/dreams) on an application cycle that is unlikely to pan out. In a year, you can get clinical exp, volunteer, and take a couple of classes with profs. Then from those experiences, you can get many good letters of rec. In short, if you really aren't ready to apply, its far more beneficial to take your time and improve your app.
I don't want to be discouraging, but spending time on improving an app is more beneficial then applying without all your eggs in a basket or however the saying goes.