The 327 is mode C, the 330 mode S. The Echo needs to decode altitude, squawk code, from the transponder. So the question should be, Can it decode mode S? (I don’t know).
Just send the altitude data you send to the 330 to the Echo directly if this data comes to your 330 as RS232 serial data. If the altitude data comes to the 330 as grey code, send the data out of the 330 to the Echo as RS232 serial data. Far more reliable than sniffing.