You need to do a ratio calculation for that. I have no idea what the spacing for a 34" is but here's what should be able to cover it if you enter the 34" spacing for the pickup.
(34 spac'g) Unknown
------- = --------
34 35
(EDIT: can't get the stupid equation to show up properly with all spacings on the screen)
Basic maths here, input the proper 34" pickup spacing, divide this by 34" scale this equals your unknown 35" pickup spacing divided by 35" scale.
Transpose this to find the unknown spacing:
(34" spacing)X35" /34" = unknown
I don't know if I'm clear, here's an example.
Let's say the pickup spacing on a 34" is 25", so:
25X35/34= 25.74 that would be your answer for the 35" pickup spacing