I picked up a pair of group 31 commercial truck batteries at Truck Pro last year for about $63 each. 1190 cranking amps, 1000 cold cranking amps at 0 deg f, 185 reserve capacity.
Those suckers really spin the engine over
I had to move the battery trays inward away from the fenders by adding some spacers between the tray and the fender to squeeze them in.
I had looked at the Optima yellow top commercial batteries at the time, but they were just a bit too tall, and I would have had to move the trays down to keep the posts from hitting the hood ( zzzzaaaaappppp
The red top optimas have the amps, but not enough reserve capacity for an engine this size
------Robert