4T Hvac unit to replace a 15 year old 3T unit(nac048akc3)

Hi All,
I m a novice to all this HVAC stuff and currently have nac048akc3. I am not too sure if its a 3T unit or a 4T unit. If its a 3T unit, can I replace it with a new carrier 4T unit? will the ducts support that?

Thanks,
Jimmy

source https://hvac-talk.com/vbb/threads/2227494-4T-Hvac-unit-to-replace-a-15-year-old-3T-unit(nac048akc3)?goto=newpost