Can you match a 3.5 ton air handler by Gibson 13 seer with a 4 ton 13 seer Rheem air handler?

You can't match an air handler to an air handler. I assume you meant a 3.5 Ton A/H to a 4 Ton condenser. The answer is no. If the A/H was 4 Ton & you had a 3.5 Ton condenser you could with an expansion valve setup. You should really match equipment when possible & I highly recommend using a qualified technician.