So do all of your route pricing out of SFO or LAX (or on Expedia, try using QLA and QSF).

In my (limited) experience, picking a city where you are going to MR to becomes frustrating... as then you are limiting the discount fares essentially to one or two city pairs. Could be a VERY LONG wait! AND picking FAT-BOS or LAX-BOS or whatever means that it technically isn't a mileage run, since you must have some OTHER reason why you want to go to that city (eg Boston) in addition to the miles. And, IME, Boston isn't often a MR candidate city. It happens, just not as often as NYC or Florida or Europe.

If you really want cheap miles, wait for the specials, and plan on Expedia out of QSF or QLA.