If you're determined to build your pecs, you may want to think about dips as that could have have some cross over to manteling.

I became a better climber when I pretty much stopped lifting weights and applied the time/energy I would have spent lifting, climbing. I still do some some push ups and dips, which seems to maintain muscle mass--that's probably a bad thing but some habits are hard to break.

If I could live my life over, I probably wouldn't have spent nearly as much time weight-lifting as I did, and I certainly wouldn't recommend anything other than the old do-a-little-work-for-antagonistic-muscles-to-avoid-huge-imbalances if you want to improve your climbing.