[RichardJ]

I used no bolts. Threaded studs are install in all manifold holes.
In this picture, not one nut has been installed and it's all resting in place. The original GM setup with only two studs, made it so difficult to get everything in place and the bolts started.

Your flanges look so similar to https://mrhotrod6.myshopify.com/prod...ant=1142523877 I thought it might be the same.