802.11a/g on gnuradio companion

i have some problems to make a system based on ofdm wich can be 802.11a
or 802.11g
so in GRC there is a block wich is ofdm mod ; i want to know if it’s
sufficient to make ofdm symbols ( modulation , inserting pilots
subcarriers , cyclic prefix …) if not what are blocks after
scrambling, encoding and interleaving  that i need to do this work ,
because in ofdm mod block there is not an information or parameters of
pilots subcarriersÂ