Hi Paula - as you might appreciate Green is quite a common name and with no middle name then your Alan Green may be rather difficult to verify.
However IF he was born 2 June 1923 then it is highly likely that he probably died 19 July 1977 at Rotorua aged 54 yrs.
The best way to confirm that he is your Alan - if you are unsure of his Birth date - might be to obtain a copy of his Death Cert at NZ $20 which should advise who his Parents were ( if known by the Informant ).
Such Cert. will also give the name of his Wife - if married - and also the ages and gender of any surviving children - ( if there were any )
Hope this may help,
regards Graham C.