I am installing a 60 amp disconnect on the side of my house and need to run power up and through my attic and down again to tie into my main panel 50 amp feeder. Do I need to run #8THHN to the entry point and then run 6/3 romex across the attic and to the panel. I am getting conflicting advice. Please help.

You lost me right out of the gate. Wew need to start on the panelboard side.

First, what is the size of the service coming into your main panelboard?

Next, you are going to use a 50 amp 240 dual breaker inside your panelboard to feed a 6/3 romex cable that will run from the panelboard to the 60 amp disconnect? What is the total (end to end run) for this cable?

What are you planning on using the #8 THHN wire for?

How are you planning on connecting the control wire from the thermostat to the A/C?

Can you get us the information off the metal nameplate on the A/C unit, please?