hey... all i gotta say is be careful with raceonusa, the reason they are so cheap is because of the poor quality.
But you said you are doing the bodywork yourself, so if you know how to work with friberglass, you could get it and lay an extra layer or two of fiberglas if it's really thin and flimsy.
Good luck to ya whatever U decide. BTW, a company called Jarco Inc. is selling a S13 conversion on eBay right now, it goes off in a few days - and they personally import everything from japan.
http://cgi.ebay.com/ws/eBayISA...47565
I've personally dealt with them before on a Celica project I did back in the day, and my friend got an RB25 from them for his hatch.