Back in the early 1980's I had a 1971 1200 coupe that I built for local club rally's. The engine was fully balanced, but stock pistons , rods etc. I had a rally cam (cant remember the make or grind) and ported and polished the head myself. Ran a single 45mm weber dual throat carby choked to 32mm and jetted to suit a lynx crossover manifold. At the time we rebuilt the motor my mate was working as a mechanic in a servo and had just pulled down a blown motor out of a toyota dyna truck, we found that the inner valve springs on the dyna fitted perfectly inside the stock valve springs so we gave them a try. After running the engine in it would rev to 8000rpm no worries and continued to do so for quite a few years. Not long after the rebuild I had to fit a race clutch as the original disintegrated when changing from 1st to 2nd at 8000 revs one day. Finally I totalled it by taking 3 pine trees out of the ground at around 80mph in a club rally. The old Datto was amazing the punishment it took, one day I hope to get another and rebuild.