There's really no magic number that will get you into a top 20 school. As said before, the higher the better. Of course, if you really have to rely on a certain number, 700 is the "magic bullet" that people talk about. In terms of your undergrad grade, I wouldn't stress too much about it. You're simply way way way way way way too far from it. If I were you, I'd take the GMAT and score as high as possible. I'd also take several courses from community colleges or extention classes (i.e. UCLA extension) to show that you do have the intellectual prowess. Your recommendation is great, but it's not going to show too much other than you're a smart person (which is also, no offense, most everyone else's letters anyway). You probably already know this: your age is certainly a factor at 36. You need to clearly show the AdComs why you need this now and what you want to do post-MBA, and make sure that it's an achievable goal. If you're geared only towards an MBA, not an EMBA, the only thing to do is to take the GMAT (and do an alternative transcript if you have the time) and apply. There's really not much else you can do at this point in your life to bolster your chance.
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