[shameless plug] Why try custom fitting it since it's a paint in the ass? How about having good ol' Mike from clearcorners.com help you modify a pair of taillights for you? At least you know THOSE will fit.[/shameless plug]
I have a 92 'teg and my friend that I hang out with a lot has an S13 Silvia (yes..Silvia K's front end too). The taillights wouldn't fit properly without a bit of fabrication to either the lights or the rear of the car.
*shudders* Back then I actually DID consider getting those Euro red/clear tail lights for my car. Then I realized how much cooler OEM was. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>