I'm not fan of Japanese vehicles (with some exceptions) but really interesting project nonetheless
Regarding the Celica, personally I like the 1979-1981 model more, as well as the GT/GTS like this (or whatever is called). It doesn't look that sporty, though.
Anyway, sorry for the little off-topic
Have you managed to convert test any of the models made with sketchup in GTA IV?
Well, the '79-81 model is known as the MA45 [part of the A40 generation]. I am quite fond of this model too, and I will most likely make one at some point. Here's what the XX version looks like:
And yes, the GTS version you posted looks like an RA64. It's essentially the same as the MA61, but with a shorter front end, as it only has an inline 4, as opposed to the inline 6 of the XX. The normal Celica also is available in that coupe bodystyle, while the XX is liftback only. Once again, I do plan to make the normal Celica along with the XX. And personally, I find both Celica's sporty looking
I have tested with conversions. I started simple and stuck the bumper of my Trueno onto the Futo, and it worked fine. I've also attempted modifications of the standard GTA vehicles (I added extra chassis detail on the faction, and I'm doing a Hakumai Coupe), which requires exporting models from Sketchup