I have plans for a project that will have an antenna rotator controller, SWR Meter, Frequency display, GPS, APRS Beacon, Morse Code and RTTY decoder. There will be output to a 3.5" LCD screen, as well as USB connection for computer control. What I know is that this is A LOT for a single Arduino to do, but how about partitioning the processes out to multiple Arduino's? Or should I be looking at an other piece of equipment?
Do you already know how to do each of those things separately on an Arduino?
If not, that is the first thing to figure out.
I suspect that driving a 3.5" LCD is well beyond the capacity of an Arduino and would be more suited to a RaspberryPI.
Do you want to do all these things at the same time? It seems unlikely.
Depending on the memory requirement of your display it looks like a Mega or Due is the right arduino to choose for this project. Only use multiple Arduinos once you have run out of memory or computing power, it makes the project at lest twice as difficult having two Arduinos.