In replacing forks its fairly easy determining for wheel size but rake is a funny one.
Is there some guide / standards showing both US 27" and also Euro 28" (700c)?
And for 1950's to early 1990's era steel-
During that timeline with so many variables, style, type and application of lightweights, I would think frame builders had some guidelines.
One could pull the original frame dimensions and maybe get something close as the maker intended.
The other is the hassle of trial and error fit / test. Inconvenient and hope of luck.
Any suggestions, old charts, guides??