Wanting to convert an old crap Suntour drivetrain of my brothers to at least basic shimano sis. He doesn't roll with a front derailleur so just looking for a shifter, chain and RD. Not sure where to start. I thought to look for the downtube shifters first, but now which freewheel do they index with?

And also, anyone (sheldon browns didnt do it for me) have a timeline for this shimano indexed shifting? When did we shift from uniglide to hyperglide? 6 cogs, to 7 cogs? 7 to 8? And when did SIS transfer from freewheel to cassette?