http://www.anvilbikes.com/images/1064634020.xls
That link will let you calculate your bike's trail.

http://www.urbanvelo.org/issue3/urbanvelo3_p44-45.html
That link will teach you a little bit about trail and different handling characteristics.

I find that a lower-rake fork on a bike that's not meant for it offers really undesirable handling. So, while this doesn't answer your question, I hope it provides some helpful information.