IIRC, the ROD 350 is a 5v TTL output? You may want to confirm this, as many Heidenhain encoders are low signal sine wave output.
The 5v versions can usually easily be subbed by one with the same resolution, Hengstler make close versions of the Heidenhain range.
If you need info or a spec sheet of the original, I have P.M.'d you a contact that you may be able to get any information on it, or a Heidenhain replacement number if you prefer.
Al.