I started out running 32:16 on my '88 Explosif but soon came to the conclusion that round here 32:18 worked better. I hardly have to do any road work in a typical 3 or 4 hour ride so the "spinniness" isn't really an issue for me.
I also ride a '94 (I think?) Explosif singlespeed and have run it 32:18 for the last month, however I fitted a 19T sprocket today which (praise the Lord !!) gives perfect chain tension with NO tensioner. Ideal :!: - so that's what I'll be running on that bike from now on.
I was going to try 32:20 anyway - the difference isn't worth worrying about.
I'm using a Surly Sprocket and a Wheels Manufacturing spacer set (both from Charlie the Bikemonger) and a DMR 32T Chainring (£4.00 ebay bargain). Chain is a KMC Z610HX (3/32" - don't bother using 1/8th chain, it's no stronger and it's heavier).
The Surly Singleator tensioner is a nice bit of kit and can be configured to push up or down (and it's quiet too).
Until you know what gearing suits you you can use your existing middle ring (if it's in decent condition) and just buy the spacer set and cheap sprockets like the Gusset ones (4 or 5 quid).
I can't recommend singlespeeding enough - I hardly ever ride my geared bike now (RM Blizzard) and I think the only place that I'm appreciably slower is on tarmac (and I don't care about that, cos I don't like riding there anyway....). On lots of of-road climbs I find I'm actually faster because, instead of just changing down and spinning up you have no alternative but to dig in and try and maintain momentum.
OK - there'll always be sections that are just unridable on a SS but you'll be surprised how few and far between they are on a typical ride. And no - I don't live somewhere like Norfolk, we do have hills here
And the silence and lighter weight is lovely too
Just go for it !!- I can guarantee that you'll enjoy it more than you thought possible
Apologies to those who have seen it before - I lurve this bike so much
Here it is 32:19 and no tensioner. Yes !!!