The frame mounts will be the same as a correct year Pontiac V8, but the engine mounts (use the mounts for '68 Bonneville) may need adapter plates depending on your new block.

Five bolt hole per side blocks should not need adapters. Three hole blocks will. I don't have a name offhand, but most of the Pontiac performance vendors (Butler etc.) will have adapter mounts.

My former '68 had home made adapter plates, I had no issues with them.