Depending on your goals and plans.
If just getting there is your main aim then I5 to I40 is probably your best bet, joining the two by cutting across to Bakersfield and CA99/58. Again overnight stops depend on a few things, whether you want to do it in 3 long days, or 4 slightly more relaxed days and of course, if you want to do any sight seeing along the way. Depending on what time you leave SF you could look at a fairly easy first day and stay over in Barstow, or Laughlin NV would be as far as you would want to aim for with an early start. From Barstow you could head to Gallup for the night or from Laughlin to Albuquerque. If you only wanted to stop twice then you would have to push on to Santa Rosa from Laughlin.
So you could go SF > Barstow >Gallup > Amarillo > Denison [3 stops] or SF > Laughlin > Santa Rosa > Denison [2 stops] Having said that there is always options, for example if you wanted to sight see with 3 stops, you could aim for Laughlin and then stop in Gallup and check out a couple of route 66 towns, the Petrified forest or even the Grand canyon.
A half's day travel -- more or less
It is 272 miles (by the shortest route) from Gallup to the Grand Canyon Village. (I-40 to US-180) although you could go in via US-89 and AZ-64.
Oh, I just read the thread.... I see you are traveling west to east?
Mark