The abbreviated form No.
comes from the word 'numero'. Note the 'dot' after the letter 'o'. It's 'No.' (with dot) and not 'No' (without dot).
Now, the pattern you follow seems to be listing the credential of a vehicle. Generally, we put colons in such context. For instance...
Name: Mr. Narendra Modi
Age: 65 years
Address: xyz...
and so on...
As you see that such listing happens with the colon and the dot is indeed necessary to abbreviate numero (to avoid reading it 'No - negation'), it'd be dot and colon with no space in between.
About space:
You do not put a space before a colon, but you do need a space after one. Source: http://www.learnenglish.de/punctuation/punctuationtext.html#colon
So, you may write like:
Vehicle Owner: Mr. Tim Cook
Vehicle Chassis No.: XYZ1234ABC
Vehicle Type: SUV
and so on...