I think I'm gonna have to clarify a few things here.
Sp3 (like all SPecial classes) isn't a stock or even close to stock class. Far from it!
Actually you're allowed to change, tune or mod (almost) everything you want. For example you could swap the engine for another engine of the the same make, or you could modify your engine by changing the bore/stroke, the crank, the camshafts, etc. The only limitation is, that your block needs a serial number on it, that identifies it as a product of your carmaker.
If you want to take a look at the regulations, you can find them here:
http://adac.24h-rennen.de/uploads/me...ng_2011_01.pdf (Sp classes start page 61, engine stuff page 64)
And because of that the Civic is a real full on Racecar and not anywhere near stock. More Info on the Civic:
http://mugeneuro.com/index.php?mact=...t01returnid=60
http://www.jasmotorsport.com/en/RaceA.aspx?Id=85&Aut=90
If you want to compare the FT to other equally stock cars, you should take a look at the V3 class as those cars will have rougly the same mods as the FT and also have 2l engines.
This chart will give you a rough idea of their abilities and specs:
http://www.vln.de/includes/download...._Matritzen.pdf