1. SS chains come in 1/8in or 3/32in – which do I need and does the chain ring and freewheel have to match?
I wouldn’t if they’re not worn. SS rings and sporckets have longer teeth to keep engaged, if the chain slips off you might need, usually chains coming off are down to chain tension.
2. In terms of chain line, if I’m using an On one SS rear hub and some old truvativ cranks (triple), what do I need to do to ensure a good chain line?
If hub has a screw on freewheel then you might be able to use spacers on the BB cups to twaek the chain line outwards but if it’s a SS frame and wheel the chainline should be correct.
3. Freewheel…shimano DX seem to be the model most places stock. Are these any good and what else should I consider?
Ask Charlie the Bikemonger he’s a font of knowledge, but there’s White Industries, Chris King, Surley it all depeonds on how much you’ve got to spend.
KMC Z7 or KMC Z510 wil be perfect
5. It’s got a QR rear hub…is it worth getting a couple of on one chaintugs to keep it in place?
Yes the Surley or On Ones will do, with the former being better.
6. bash guard to help keep the chain on?
You shouldn’t need one if you chain tension is good.
7. Lots of hills in ramsbottom. I’m reasonably fit so what gear ratio??
Not sure, I rode with Donk on his SS at Christmas and that was at Rivington Pike, you can contact him and ask but think he was on a 32:16. I’ve got 32:18 on mine but I like to spin.
While I’m here. Inbred max fork travel is quoted as 120mm. I have some spare 130mm bombers, which I’d like to use. Anyone run similar and find it OK?
Not sure but you could run 10mm more sag.