If you have the necessary power supplies available to use with a transistor level shifter, why would you need a charge-pump-based level shifter like the MAX3232 or MAX232?

There is, of course, the classic MC1488 driver. That uses a bipolar supply, however, and the reason most people want to use a charge-pump-based shifter is because they don't have a bipolar supply available.

The receiver is another story. Since levels between 3 volts to either side of GND are ground-ruled out, hence, invalid, all you have to do is to sense, in a receiver, a voltage above 3 volts. This, of course, is not a complete solution and I'd advise against it, but some people have "gotten away" with it. If you use a Schmidt-trigger and a resistor-biased/attenuated input, you can do that. Again, I advise against it.

RE