Will a Pontiac 2.8 or Chevy bolt up the same as jeep in Jeep Comanche?

No, a Pontiac 2.8L V6 and a Chevy V6 will not directly bolt into a Jeep Comanche without significant modifications. While both engines might be of similar displacement, their bell housings (the part that connects the engine to the transmission) and engine mounting points are different from the Comanche's original AMC engines or even the later Chrysler engines used in some Comanches. You'd need custom motor mounts, a custom transmission adapter, potentially a custom driveshaft, and likely other modifications to the cooling and exhaust systems. It's a major undertaking, not a simple swap.