Japanese License Plate Help

[SilverSuby]

I have a general idea of what the numbers stand for I'm looking for a license plate that is authentic (white with green letters) but I don't know what the top right number is for or the four large numbers are for. (cc displacement I think)

[Yamazaki]

The four large numbers are just whatever. They also don't have to all be there. You can have *8-65 or **-45 for example. I see a lot of **-*1 and other low numbers. Those are personalized plates. I was going to get *4-01 for my S401, but didn't get around to doing it in time.
The top right number will be the classification. The most common are 3x, 3xx, 5x, and 5xx. Those are all personal vehicles. What you get is based on engine size AND dimensions of the vehicle. Normally 2.0L and less will start with 5. But the GD/GG and newer Imprezas, as well as the BL/BP Legacys start with a 3 despite mose of them being 2.0L. Company vehicles will have 400 and the big transport trucks have 100.

That's a VERY basic rundown of the system. Here are some pictures (click to view) of example cars (note: all are 2.0L vehicles).

Example of a personalized plate (on an actual S203):
https://sl-i.net/FORUM/images/imported/2011/12/th_DSCF1807-2.jpg (http://i426.photobucket.com/albums/pp350/yamazakisubaru/cars/Impreza/DSCF1807.jpg)

A GC TypeR Impreza:
https://sl-i.net/FORUM/images/imported/2011/12/th_DSCF0512-1.jpg (http://i426.photobucket.com/albums/pp350/yamazakisubaru/cars/Impreza/DSCF0512.jpg)

A BL Blitzen:
https://sl-i.net/FORUM/images/imported/2011/12/th_DSCF1270-1.jpg (http://i426.photobucket.com/albums/pp350/yamazakisubaru/cars/Legacy/DSCF1270.jpg)

A BE Blitzen with a Chargespeed bumper:
https://sl-i.net/FORUM/images/imported/2011/12/th_DSCF0574-1.jpg (http://i426.photobucket.com/albums/pp350/yamazakisubaru/cars/Legacy/DSCF0574.jpg)

[SilverSuby]

So I have a 2.5L 3x or 3xx would be my top and i can put 251 for EJ251 engine. Don't they have to be white with green lettering for private vehicles and yellow lettering for larger company vehicles, thats what I found on another forum.

[Yamazaki]

No. The white with green is correct, but then there's yellow with black lettering (Kei [light] cars), green with white lettering (almost all taxis), black with yellow lettering (almost all semis, dumptrucks, heavy haulers), and I'm sure there are more, but I can't think of them at the moment (they aren't common).

[hansvonaxion]

I think the foreign vehicles (embassy cars and what have you) are white on blue with "?" in place of the hiragana character... kind of appropriate in this case.

[Yamazaki]

So I have a 2.5L 3x or 3xx would be my top and i can put 251 for EJ251 engine. Don't they have to be white with green lettering for private vehicles and yellow lettering for larger company vehicles, thats what I found on another forum.
I occurred to me that I didn't really answer your question. Yes, a 3xx plate and the *2 51 (don't forget the dot) would be my advice for a "realistic" plate. For a truly accurate plate, just follow this guide: http://www.k5.dion.ne.jp/~nplate/list/main.html

[SilverSuby]

So I have a 2.5L 3x or 3xx would be my top and i can put 251 for EJ251 engine. Don't they have to be white with green lettering for private vehicles and yellow lettering for larger company vehicles, thats what I found on another forum.
I occurred to me that I didn't really answer your question. Yes, a 3xx plate and the *2 51 (don't forget the dot) would be my advice for a "realistic" plate. For a truly accurate plate, just follow this guide: http://www.k5.dion.ne.jp/~nplate/list/main.html
Do I need to change my language settings I can't read japanese...

[Yamazaki]

Try babelfish or something. I'm not sure how well it'll translate though...

The main problem is - you're asking about something specifically Japanese. The reliable info is going to be in Japanese. It's like the Japanese guys who are into American muscle cars; they have to be able to read English because that's where the good info is.
Basically, (I know this doesn't help, but I'll say it anyway since it's what I believe) if you're truly interested in an aspect of another culture, you really need to know the language of that culture to fully learn that aspect you are interested in.