I have a DML36X lathe and I'm thinking of converting it to a swivel head, does the upgrade kit include a spacer for the tailstock? Also, will the CL3/B bowl turning attachment fit this same lathe?

The tailstock does not neeed spacing as the swivelhead unit and base are the correct height for the tailstock (9" centre height).
The CL3/B does not fit the DML36SH or upgraded DML24X - but there is a similar accessory called the DML-BR which is available and does the same job in a similar way.