yes. you will not be able to properly tune a 13:1 setup on pump gas without fear of detonation in summer in FL.

if you live somewhere that is more moderate year-round, it might be possible, but with 100 degree heat and outrageous humidity, you will get detonation.

the PR3 or P30 (mid 11:1) is perfect for a solid N/A daily driver, but if you wanted to go slightly higher, a 2-layer headgasket would do the trick.

*EDIT*
ok, so i may have exagerated slightly. it is POSSIBLE to tune a 13:1, but IMHO, it is way more trouble than its worth... and you will just keep shifting your powerband upward, so on an LS bottom end, that doesnt like high rev's with its 1.54:1 rod:stroke ratio, this is actually counterproductive.