A group 27 should provide plenty of starting amps. If it's a chevy with the side posts get one of those, or adapters. Costco, walmart, sams, all good and cheap batteries.
Why is it missing? Stolen? Borrowed?
Chris & Sherry Brown -
2005 Itasca Sunrise 31W - W20 and 8.1
2021 Chevy Spark Toad