Will a Buick v6 bolt to your 1987 automatic montero 4x4 easily?

No, a Buick V6 will not easily bolt to a 1987 automatic Montero 4x4. The engine mounts, transmission compatibility, and overall engine configuration are significantly different. Custom modifications and adaptations would be necessary to make such an engine swap work, including custom motor mounts and potentially adapting the transmission or using an adapter plate.