Measuring for Springer Fork

[CannonCam]

I have a mid 50's Evans Colson Sonic Scout with a bent fork that I'd like to swap a springer on to. Looking around I can't really seem to find one "standard" way these aftermarket fork companies are measuring them as they are all over the place. Any advice on what measurements to take?

 

[Fv2]

You should only need to know steer tube lengh.

 

[SSG]

Steer tube diameter also. 1" threaded is what you find on vintage bikes, although it's still found on a few of the cheaper modern bikes, you might also come across 1-1/8 thread-less forks to fit newer frames.

 

[Starnger]

Steer tube diameter also. 1" threaded is what you find on vintage bikes, although it's still found on a few of the cheaper modern bikes, you might also come across 1-1/8 thread-less forks to fit newer frames.

Or 1-1/8 threaded, like on later Dyno Glides.