When doing custom front ends, here's some info on how to determine the proper length of the forks.
Determining Your Fork Length
Jeri's Springer Front End - Fork Length
RB Racing Rake and Trail Calculator
http://www.phred.org/~alex/bikes/Fork%20Re-raking%20Summary.pdf (or download from attachment)
Determining Your Fork Length
Jeri's Springer Front End - Fork Length
RB Racing Rake and Trail Calculator
http://www.phred.org/~alex/bikes/Fork%20Re-raking%20Summary.pdf (or download from attachment)