Thanks for the reply Henrik.

In reference to #2, that's what I meant. I know SERIN/OUT is slower, but it won't matter for my application. Is it as simple as just running the UART I/O to the SERIN/OUT and then when I want to send something, I just put "SEROUT pin, mode, blah, blah, blah....." Also, can I or should I use SEROUT2? If I understand it correctly, the only difference is flow control?

In reference to #4, the external UART IC is only 3.3V. It states that it's an 8mA drive, but nothing on the input. When I'm using SERIN, the 4550 should be floating and only accepting the UART data, so 3.3V should be the max and I can connect the input directly. When I'm using SEROUT, the 4550 is driving the data at 5V and I would need a resistor, perhaps 1k?. I've never done this before, is my understanding correct?