Which new battery to put in truck

[FL71C10]

I am putting my truck back together and am close to firing up the motor. I need a battery and was wondering what size some of you are using. It seems like the application charts are all over the board. Some are suggesting a side post bettery, some top post, and the group or sizes all vary.

I've got a 71 with a 350 automatic, no air (although I want to put aftermarket air in at some point), I've got a late model internally regulated alternator if that matters.

Any suggestions?

Thanks!