HI Phill
Looks like a scratch built model and possibly not based on any particular ship.
I am posting a picture of my HMS Grenville a 1:96 scale destroyer from the 1940's. its 3' long and about 3" wide.
If you wan't to detail your model I suggest you look on Google and find pictures of IJN destroyers and choose one of a similar design. I suspect you may need to rework some of the superstructure to get the scale correct. Both Traplet and Model boats offer plans of destroyers which may help.

Hi,
Are you talking about the Aerokits Sea Rover? because that wasn't 41'' long, more like 29'' and I don't recall seeing a GRP hull for it- the original was a wood kit. However, Lesro Models do the plans for these boats- I bought a Sea Rover plan from them some years ago. Might be helpful to post a picture of the hull.
Ian