Those valves appear to be the ones sold back in the 1990s, with the 30-degree faces. Maybe pull one out and take a peek? The contemporary thought in those days was that the shallower valve face angle increased breathing earlier during the intake stroke and reduced exhaust stroke pressures for the same reason. In this particular engine, this only works if the bores are increased to at least 64mm (825cc) and the head relieved accordingly, otherwise the intake valves are too shrouded along the cylinder wall. This item, BTW, is why the better head gaskets out there (like the Honda or Cometic) have an irregular shape (not round), flaring a bit around the edge of the intake valves: it deshrouds them slightly. You can also add a bit more yourself into the cylinder wall near those valves, just be careful to only go down as far as the top ring's upper reach, or it will lose compression in the trade.
The springs appear to be stock pre-K3 type, although it's hard to tell if they are the round-lipped keepers or the square-lipped ones: for my $$, I always use the latter as they don't have the history of pulling through their grooves, dropping a valve at an inopportune moment. The post-K3 springs are tapered and have lower seat pressures, but they also have a lower redline rating because of it. The early springs (with stock valves) could manage 10,500 RPM with stock cams, while the later ones run out of clearance around 9200 RPM.
