Converting 80s bike to indexed shifters I've just bought an early 80s steel framed bike with unindexed stem mounted shifters. As I plan to use the bike for commuting, I'd like to change the rear mech to use trigger shifters.

I'm not so bothered about converting the front mech at the moment, although I assume it's a similar (if not easier?) process.

The rear dérailleur is a Shimano Tourney (couldn't see a date - it's not new though) and there are 5x2 gears. The gear spacing is definitely less than 10mm although I've only tried to measure it with a ruler.

I've read lots of guides about doing this conversion, but I'm a little confused about what I actually need to do in my case. 

I think the rear dérailleur is fine and doesn't need replacing. And I think that all I need is some trigger shifters, but I'm worried about the indexing and spacing. I've read that faster triggers are less likely to suit the spacing, but I don't know why? 

Am I on the right lines? Thanks!
Stick with the friction shifters. Changing a non indexed bike to index is expensive and unnecessary. 

You will need a new dérailleur to index correctly along with a rear wheel that can mount a cassette (assuming your running a freewheel). You will also need new shifters which if your running a road bike are very expensive. 

If you must have index shifting I would recommend a late 90's bike with index shifting already installed. They are generally very cheap second hand and don't require a complete overhaul.

I have an old 80s Apollo road bike that I use for wet weather commuting. I was thinking of doing the same thing and upgrading to indexed shifting. I installed new wheels (Mavic Aksiums) and added a seven speed cassette to the rear hub. I stopped there because the bike ran brilliantly. The new wheels are much lighter than vintage wheels and the hubs are much smoother. A worth while upgrade.

You will get used to using friction shifters very quickly. I actually quite like them now even for commuting.