This is one of the reasons why we believe the two are SPARTANs. To answer your questions, yes... there were more than 75 Spartans trained.
I'd like to point out that while there were 25 SPARTANs on the Reach-op, there were not enough Class-Is there.
33 Class Is survived augmentation.
33 - Sam - Kurt - Randall - Maria - Cassandra - Sheila - Jai - Mike - Adriana - Jerome - Douglas - Alice - *unnamed S-II from Halo Wars* - Keiichi = Nineteen SPARTAN-IIs at Epsilon indi. Minus John, Linda and James and it's SIXETEEN Class-Is on that pelican.
That means that for there to be 25 on the Pelican, another 8 or 9 (depending on if you think Keiichi survived) must appear. Enters: Class-II
In 2537: ONI kidnapped an unknown number of children to become the second batch of SPARTAN-IIs. With candidate numbers starting at 151, there may have been as many as 200 candidates. In 2545, the recruits undergo Augmentation to enhance their bodies Mentally and Physically... Some - Yasmine for instance - died due to complications.
My evidence shows that there is room for Class-IIs, and with the appearance of two "Sierra"-number tagged special-forces members undergoing an orbital insertion to Reach and their Pelican crashing just like Bravo 1, it seems quite likely that they were present.