-
26" MTB rims is probably a good idea, and no doubt cheaper than a pair of HED's. tyre choice for 650c clinchers appears to be somewhat limited though. would 650x23 be too small for a wide MTB rim?
again this is all speculation at the moment until the frame arrives, hopefully this week, I have a tracking number now but the parcelforce website still isnt showing anything.
geo should be ok, i hope, i'm currently riding 56.5 square fixed so this won't have masses of seatpost showing above the seattube extention.
groupset wise I was looking at Black 105, or something Sram. mainly based on looks and price.
Dry-
650x23c tire won't work on the MTB rim - MTB rim is 559mm and 650c is 571mm. There is only two tires on the market bigger then 650x23c and both of them are only available in USA and some frames with tighter clearences might not even take them.
There is plenty of road tires for standard MTB rims (559mm), a nice comfy 25mm tire on a wide rim (would probably measure 26-27mm once mounted) would probably give you nice tight clearences. You should still check if the brake reach will be fine (the brake pads will need to sit only 6mm lower then with 650c rims).
Silver seat post and stem, compact bars, black saddle and tape (maybe even some colored tape to match the frame), tan wall tires and black 105 would look ace IMHO!
FredyCro
If it is 650c (571 mm), you might consider building a wheelset based on a 26" modern MTB rims (559 mm, wider rim, wider tire, low spoke count would look cool). It will definitely be cheaper, make you tire choice easier and should be OK with geo, clearences and brake reach (stuck in a 26" MTB wheels with no tires mounted to check this).
The geo looks quite challenging for a road build, but with a layback seat post might be ok - you might end up with a big saddle to bar drop depending on how much seatpost you need showing. What groupset are you considering?