We have some very good guys up here that should chime in, in my opinion it does appear to be a Donzi or a clone. Like you stated the steering dates the hull to an earlier time, seemingly originally setup for a Volvo out drive. Look at the upper right hand side of the transom, see if there is a hull ID#. Also you could try to look under the dash and possibly up by the bow inside for any numbers in magic marker. Let us know what you find!
Phil
No matter what your beliefs are "GOD BLESS AMERICA"
Fully retired marine tech near 60 years in the biz.