I believe the turbo is serviced separately from the Lister overhaul set... best bet is to find a turbocharger reman outfit to do the repairs. Take a look at the turbo manufacturer information - model and spec numbers from your unit. Failing that, it may be possible for you to pull the old seal, carefully measure, and source a replacement based on those measurements and the application.
We can supply most of the normal Lister overhaul gaskets for the HRS6.
dieselgman