I myself had problems insuring a grey import sports car which was very similar to yours in its time (1996 6th Gen Toyota Celica, 2.0 SS3). I went with Direct line in the end as they were the only ones who would accomodate me, they ended up putting it down as a custom model (GTS) and my premium was £413 fully comp and they insisted that some sort of alarm was fitted (There was'nt one fitted due to low car crime in Japan) So I fitted a cat 1 Alarm/Mobiliser with an volunatry excess of £400 (I was 32 at the time with a clean licence), then the next year it went up to £500 even though I had 9 years no claims, then the next year it went up again to £600 even though I had never claimed.
I think you'll be spending a lot of money on repairs to your suspension as well (mine needed new ball joints every 9 months with the suspension being so hard and britain's roads being what they are).