Go for it!
Dunno about FcÂ´s though... but...
When my brother got his FB, we did lot of research about rallying FB. In Usa and Aussies, they have raced alot with those and FcÂ´s too. They had weird 4wd systems in FcÂ´s.
My opinion is that Fb is very good car on gravel. And in tarmac of course. It is very neutral to drive in gravel. I think one of the best for that time period. Compared to (for example) Ford Sierra, which is crap.
One problem is ride height and suspension travel. It needs to be higher and needs lots more "in" travel. Suspension will hit bottom quite fast.
Second problem is weight. Fb is very heavy car for old car.
I dont know if you need competition wheels yet. But you need some brake upgrade and engine cooling needs to be very good.
Other than that, I think that FbÂ´s and FcÂ´s are very good weapons for gravel too
At the moment, I have weird dream to get RX-8 to gravel
Well, just few of my thoughts...