A repairman is installing a carrier fy4anfo48 inside/ 24aca348a300 outside are these 4 ton units and i had a 3 ton unit, downstairs. Payne 0608a71992 inside/ carrier 38tkbo36300 outside, and i had a 2.5 ton unit. So are these truly 4 and 3 ton units and what ducting changes need to be done with these bigger units. My home is 3400 sq ft. your thoughts, i know nothing in this area

The outdoor units are 4 ton and 3 ton.

The duct changes will have to be calculated on the job. There is no way I could even guess as to what you have and what you might need since you are going with slightly lager units.

You hired these people to do your job. If you do not trust them to do the job correctly I would hire someone else.

NOTE I do not know where you live but that is a lot A/C for 3400 sg. ft.

Did they do a manual J?

Did they do a manual D ?

You might ask the how they sized the unit and sized the duct work without doing those calculations.