ICL3232 and SN75C3232 difference
Looking at the ICL3232 datasheet we see:-


  Maximum Data Rate RL = 3kΩ, CL = 1000pF, min 250 typ 500 kbps


and in the SN75C3232 datasheet:-


  Maximum data rate RL = 3 kΩ CL = 1000 pF min 250 kbit/s


So it seems there isn't much difference between them. 

The SN75C3232 also specifies a minimum of 1000 Kbps with a supply voltage of 4.5 to 5.5 V, so if you are running it from 5V the SN75C3232 is guaranteed to meet your requirements (the ICL3232 may do as well, but you can't complain if doesn't).