Here`s hoping someone can help. The forks on my trike that I`m building are 37mm x 31" long, and threaded at the top. I think they are off a GS 850. I am looking for longer forks are there any out there that will fit my yolks as I don`t want to change them.

Depending on how much meat is available in the yokes, a possibility might be a slightly larger dia (and longer) set of forks with yokes opened up to suit ?? (which is 'changing' them in the machining sense, but 'not changing' them in the replacement stakes)
Maybe have a look around an autojumble? Kempton Sat 28th Jan.