I don't have spacer length.
This is what I used for bolts:
6.0L Exhaust Manifold to Heads:
12-Point Flange Head Cap Screw:
Type 450 Stainless Steel, M8 x 1.25 Thread, 40mm Partially, Threaded Length, 170,000 Minimum Psi
96242A999
Turbo to UP-Pipes:
12-Point Flange Head Cap Screw
Type 450...