Threadless on "old-school" steel?
 

I have a '98 reynolds 853 Dean. It's currently running a threaded headset. I should know the answer to this but I don't: can I, with a different fork, convert it to threadless? Or is the head tube/resultant steerer tube too small for threadless?

Thanks!

You can convert to threadless with a new fork and new headset. It's probably going to be 1" threadless, though, which will limit your options (fewer choices of forks, headsets and stems).

No "probably" about it; only a 1" steering tube will fit into a 1" head tube.

That being said, many threadless headset manufacturers offer 1" models; I have a 1" Chris King on one of my bikes.

Stems are even easier; all you need is a steering tube shim and you can use any 1-1/8" stem on that 1" steering tube.

My gold/black SS is a c.1980 french steel frame with a 1" threadless all carbon fork. Easy conversion, but not free.

Sweet. Thanks, folks. :)

Actually depending on whet you want to do, you can just get rid of the quill and use threadless stem by removing the quill and replacing it with an adaptor, which mounts inside the steering tube like quill would and build up a threadless setup above. I've done it on couple of bikes to get the threadless stem flexibility.