What can you keep?

Three questions about the system you have and the unit you were quoted. The answers come from the manufacturers' own documents, and every one of them is cited on the model page.

Or start from your brand

• American Standard American Standard has not published, in the bulletin read here, a rule about using an existing R-410A coil with an R-454B outdoor unit.
• Carrier Your existing R-410A indoor coil cannot stay. Carrier states that full furnace coils are not interchangeable and that the refrigerant the indoor coil is designed for must match the outdoor unit's.

This is a starting point, not an approval. Everything here is read from published manufacturer documents and dated, but only the licensed contractor who signs your installation can approve a specific system for your home and your local code. Take the citations on this page to them and ask.