I don't know what the best one is but I use a Rural King/Exide DT-75 60. The regular price is $50 but Rural King has frequent sales and sells the battery at $45.
http://www.ruralking.com/battery-630-cca.html
I have bought probably 20 RK batteries in the 5-6 years we've had a store in our area. I had one fail just inside the 12 months and they replaced it free. Another failed in the pro rated period. I never took it back. The rest of them have held up well so I have no idea how long they will last. Besides, how cn you beat paying $45 for a battery?
You may have to slightly modify your battery cables to fit.