For the wheelbase they're M6, you need 10mm + the thickness of the mounting plate. Assuming most mounting plates are 3mm use washers and 15mm are ok. If you use all the t-nuts you'll need 4 of them. The pedals are M8 (I used 20mm) for the rear holes + washers and lock nuts (one bolt per pedal). For the front mounts under the pedal plate you need two M6, 22mm + thickness of the mounting plate, think I used 25mm ones with washers.
You can download the manuals and they have the mounting instructions.