Much of what you need to accomplish to master GMAT verbal is to become accustomed to analyzing verbal questions choice by choice and seeing what's going on in the questions. So, even though LSAT questions can be a bit different from GMAT verbal question, you can develop your overall verbal skills by using LSAT questions.
That said, if the reason you're asking about LSAT questions is that you've run out of GMAT verbal questions to practice with, you may be going through verbal practice questions too fast. To maximize the results you get from your verbal prep, you should spend a fair amount of time on each choice of each question, and if you use the questions in that manner, you get a lot more out of each question and don't need as many practice questions.
In fact, it's likely that you could learn a lot and develop your skills by going back and analyzing GMAT verbal questions you've already answered. The fact that you already know the correct answers doesn't keep you from learning by analyzing the choices to see exactly what makes them incorrect or correct.
For some more GMAT verbal training tips, see these posts.
How to Score High on GMAT VerbalThree Key Practice Tips for Mastering GMAT Verbal