I brought home a pristine Bridgestone T700 with a 21" frame, which turns out to be a wee bit small. I'm wondering whether it is better to seek out a longer seat post and stem to make the bike fit me, or to give it up and look for a 23" frame, which would (most likely) be a tight fit and may or may not be as well-preserved. Any suggestions/recommendations are welcome. The original seatpost is SR, 27.0mm

Do Both.

Thats a nice bike. Post some pics.

Play around with the seat height. You can try raising the stem or replacing it all together. Or go the flat bar route. Im sure you can make it fit you comfortably

If it's only one size too small you might try a longer stem, maybe a different handlebar to suit your preferences for reach and drop.

I see a lot of pros and wannabes locally riding frames that are technically too small, but they want the exaggerated drop from saddle to handlebar. So they use longer stems to set the reach appropriately.

No way I my neck could handle that kind of drop so I have no idea how that setup affects handling or whether a too-small frame might still have problems that could affect the knees, hips, etc. Might also be appropriate to change crank lengths.

I still prefer the old school fit -- more stretched out, maybe 2" or, at most, 3" drop from saddle to handlebar.

Seatpost and stem are raise to the max allowable...

I grow them all the time but it's not for everyone. Here's my Bridgestone 400 that's technically too small. Longer post, more quill (or 90 degree), more extension, 44cm bars and 175 crank arms are my usual routine. 59cm ctc is what I prefer and I'm usually growing 58s. This one measures 57cm ctc and is the limit of what I'd want to grow.

Very pretty - plonz, what seat post do you use?

Sweet bike.

I'm of the opinion that the worst thing is a bike that *almost* fits.

You know how cool it is, you get a taste of how it rides, but it's *just* not right. The proverbial carrot dangling in front of you.

Why thank you! The seat post is a plain, no-frills Kalloy. Pretty boring but come in a lot of sizes (incl 27.0) and a 350mm length. Right around $20 IIRC.

For something dressier, check out the Dajia 1b seatpost. A little more expensive and also made in 27.0. Dajia length is 300mm which is still long enough for my applications and saves some weight over the Kalloy. I got one at Velo-Orange a while back.

At slightly less than 58, this frame is really too small. I love riding it though
1983 Colnago Superissimo on Flickr

The largest frame in the stable is 61. Still more than a fist full of post. This frame is at the upper limit for me.
2010 Langster Steel 61cm on Flickr

My target is 60 but event that looks a bit small when judging by post extension.
P1040420 on Flickr

I think with touring models like the T700, and you are in between sizes, go for the larger one.