LSAT books, particularly Powerscore RC and Powerscore LR, can be effectively incorporated into one's GMAT studies. I used these two books, along with the LSAT SuperPrep. In my opinion, the RC questions are excellent. LSAT questions are considered more difficult than their GMAT counterparts.
I would, however, advise you to pick either the Powerscore LR or Powerscore CR - not both. The LR version is identical to the CR book, except that it's much larger and covers more topics. Purchasing both the CR and LR would be a waste of money.
It's also worth noting that Powescore LR and Powerscore RC are expensive, difficult, and take a great deal of time to finish.
Here are some general discussions on this topic:
lsat-for-gmat-95577.htmlusefulness-of-lsat-books-materials-80818.htmlusing-lsat-material-to-prepare-for-cr-94478.htmlpowerscore-logical-reasoning-bible-debating-it-61469.htmlgmat-verbal-prep-using-lsat-book-92815.htmlAnd here are reviews on the three books that I mentioned above:
review-of-powerscore-s-lr-bible-96013.htmlreview-of-powerscore-s-lsat-rc-bible-86718.htmlreview-of-the-official-lsat-superprep-96276.htmlThere are, of course, many more discussions on this topic scattered throughout GMATClub. But these links provide enough information to make a decision.