Building a bike out of a pair of shif- I just wanted a gravel bike

-> break left hand shifter on road bike
-> get fed up of using bodged thumb shifter and upgrade to 11 speed
-> spare (now)1x10 mechanical sram shifters
-> time to build a gravel bike

Unfortunately actual gravel/adventure/cross/whatever frames are too expensive so converting an old mtb will have to do. Also they look cool. Enter ebay find which I probably payed too much for, but I like the paint and the triple triangle, a 2001(?) GT Zaskar Race:

Key features which will determine the build:

• came stock with a suspension fork, more on that in a second.
  
• somewhat inexplicably has a 68mm BB, so I can have road Q factor yay!
  
• IS disc mount so the canti studs are getting left alone.
  
• which allows for a wheel size other than 26", it should fit 650b*47 or 50, maybe 2.1".
  
• since the shifters that started it all are Sram, I can use any generation road 1x or 10s era mtb derailleur, probably more choice than is healthy.
  
  

The shifters in question, attached to some spare handlebars and a rather nice Kalloy Uno which unfortunately I will probably not be able to use because the frame is looooong.

However, before it can become a bike it needs a fork. Apparently the stock fork was a Rockshox SID XC which has an A2C of 450mm, so I need something in that range right???
The only production fork I can find that seems like the right thing is the Surly ECR in 27.5 which has 447 A2C and every mount I could ever want (I want lots of mounts). The only downside seems to be that it weighs almost the same as the frame so the ride might not be super SuPpLe, but I suppose that's what happens if you can't afford custom. I hope I'm not missing anything?