I'm looking for a used fork for a late-70s Raleigh Grand Prix. New forks won't do because they have less rake and I already have a bit of wheel-toe overlap.
Fortunately, there is a bike shop in my area that has lots of used parts from old bikes, so I should be able to find something. However, I want to go in well-prepared to make sure I get a compatible fork (I'm planning to do the work myself so I don't want to walk away with a fork only to find days later that it won't fit).
What measurements do I need to take to make sure that my new fork will be compatible with the frame?