5.9 Mag stock LB or rebuilt SB

@AJ/FormS
I like what you’re saying and I do like the thought of the high CR. Can I do that on 91 octane? 1200ft elevation, not much humidity to speak of and hot as hell. At least right now. Not that it would be driven in the summer too much.
Would you start with the rebuilt SB or the 96k mile long block.