29. If you park south of the stadium then go with 49.
I agree with Soupie. Those aren't great sections. The face value of the tickets in sec 25 are the same as the face value in those sections. So if you're able to find tickets directly from BYU look for sec 25 rather than 29.
Since you're looking for BSU tickets note that it's going to be a hard ticket. BYU released a couple hundred of them today. It seemed that every couple of hours they released a few more on BYUtickets. Perhaps they release more online tomorrow too??? Who knows how many they have left? Probably worth calling the ticket office tomorrow? Note that Stubhub might still be your best bet (even with their ridiculous fees).