I have seen statistics correlating SAT performance with IQ.  Are there
any studies correlating performance on the LSAT and GMAT with IQ?  I
need to know both the correlation and the accuracy.  Thanks.

Both LSAT scores and GMAT scores can be used as evidence to qualify
for Mensa membership:

http://www2.misnet.com/~rick/mensa/tests.html

Usually one can find the percentile of the population which scores
below a certain score and then use that percentile to calculate IQ.
(ie 98th percentile equals 132 IQ).  The problem is that only a select
higher than average IQ segment of the population takes the GMAT or the
LSAT so 98th percentile on those tests correllates with a higher
percentile when compared with the general population.
Look at the home pages of various high IQ societies which are more
selective than Mensa and you can get an indication of where a certain
LSAT/GMAT score ranks a person in comparison to the general
population. Example. 99.9 percentile equals a 151 IQ and a 746 GMAT as
can be seen by looking at the "triple 9" society homepage.  A 99.99
percentile equals a 160 IQ.  Look at all the societies and you can
make a chart that covers IQs from 125 to 160.