A LONG time ago I polled several lists on the topic of what rod people favored for battery welding. 7014 came in first with 7018 a very close second, and 6011 (? or maybe 6013 - which ever is greater penetrating) a not too distant third.

Number of batteries will depend on rod size. I've been told the 3 work better than two in most cases.

No idea on how long b4 you can't start your repaired truck.