I dont understand why you wont consider 130 rear spacing if youre just building a singlespeed.
You'll have more options in terms of rear wheels you can use just by using spacers.

I got a Cervelo P2SL with carbon fork from ebay for $400.
Its a time trial frame. It had internal routing. Aero tubing.
Turned it into a singlespeed. I flew on that sucker.