If you are using the manifold from the original motor, the ports are smaller than the 261. Rings for the 261 will be too large. In the original photo it looked like the intake wasn't meeting the head. If an alignment wring hangs up, it will not seal. To seat it I lossen the bolts between the two manifolds and sfter it is mounted I tighten them again.
By the way I don't think there is such a procedure as "planing" the alignment rings. They are shorter than the combined depth of the two grooves.
