what if i am operating at 11 Mhz? as the clock timing
I hope you mean 11.0592MHz and assume you are going to use a 12 clocker.
The slower your clock, the more forgiving the system will be if you still use fast components on the other end
e.g. if you slow down the clock till !RD is 100 ns wide that signal still has to make the data available on P0 when it disappears. If you use 70ns access time RAM, you then have 30ns to play with, but if you kept the 30ns RAM from the faster clock you would get an advantage.

Erik