You can not implement multiple memories that do not share the same address and control bits.
A Stratix III MLAB has 10 ALMs. When you use a MLAB as memory, each of the ALMs can be configured as a 32x2 or a 64x1 wide RAM. Thus you can accomodate upto a 64x10 or 32x20 memory in one MLAB. All the ALMs share the same address bits. Hence you can not combime multiple memories with different address bits and implement in a single MLAB.
MLABs can be used to implement either memory or logic. When you are using a MLAB as memory, you will not be able to use the unused ALMs in the MLAB even if you do not use the full capacity (640 bits) of a MLAB.