Summary: This is a program I briefly investigated which theoretically has all the mechanical relationships between parts. Eg: You pick the frame, and then pick the parts that will go with it.

Conclusion: Does not work well enough to be useful for me. I started with "Frame", and I saw the Surly LHT. I got as far as "cassettes" and noticed that there were zero 8 speed cassettes. So I tried 9 speed and tried to filter on the 36 tooth one. 11-36 In order to really work, you'd have to choose a whole groupset. What I really want to see what could be done with a familiar frame, like Norco, and put a whole groupset on it.

So it could know that Surly has 135mm dropouts. The acid test is to go to wheels. It came up with 2 wheel sets, both 135mm dropout. But no price or merchant.

In order to use my system to build a bike, you'd pick each part according to the frame specs: It would be easiest to pick a whole groupset. Eg: Sora. I see crank, cassette, deraileur, shifters levers. R3000 of Sora drive train. R3030

  There seems to be a website called https://pcpartpicker.com, and they refer to a site called https://cyclingBuilder.com

 - I found Surly on list.

  Frame
  Handlebar
  Choose Bar Type
  Choose Grips
  Choose A Stem
  Choose a Front Brake/Shifter
  ...

  So now I went to the second item, which is Handlebar. I chose
  FSA Adventure Compact 31.8 x 40 cm Drop Handlebar

It tells me I can buy one at Chain Reaction for 60.99 + 86.98 shipping
 - they have some concept of sending an alert if the price drops below a "set" point
 - they have 3 filters. Width: 400, 420, 440, and have the weight.