Steering rack extensions for MX5 build..

[Johno]

Hi all,
I got the steering rack extensions made as per book ages ago before I realised they were too long. Going to get them re-machined this week to suit MX5 ends from the donor. The question is how long should they be and what size thread.
The reason I ask is I haven't taken my donor to bits yet so just being lazy I guess...

thanks Johno