Ok yeah no way rego places will give out the owners details. The only way is if you see them drive past and follow them home.
if you cant have numbers and letters on bikes then you cant have PE400 then. and PEFOURHUNDRED is obviously too many letters.
Yeah if no one else has PE397 and it was a number previously issued then sure you can have them. You would have to go in with your dad though. If you just ring up and ask has anyone got PE397 if they say no then thats ok but if they yes, thats all they will tell you. It might be that they are still listed under your dads name but if your on the phone and they say 'that number is taken' and you say 'ok my name is Michael Ryan, would the number just happen to be listed under my dads name', they probably still will not tell you. You would have to go into the rego place with your dad. Chances are your dad still knows if the number is or isnt still owned by him. Usually the rego places have to send you a letter to say they wish to re-issue your number. They have to get the owners permission first. if the bike has not been regoed for many years there is still a high chance it is still listed under your dads name.