If you expect an answer then you need to list exactly what make, model, year, and engine size you are talking about. GM makes many different cars with many different engines.
You can transplant most any motor into your Pontiac, which had a gm block originally by the way.
Yes it is.
It's an Olds 403.
Can you put a 350 gm motor in 97 ford f150
easiest method is to pull the head and measuure the bore and check with the local machinist
This motor is not compatible with diesel engine parts. As this motor is generally used in smaller GM cars that are a little more than lightweight. You would need a motor for a GM truck to match with diesel parts.
Pull the motor or pull the transmission, one of them has to come out.
The 4.3 is a V6. If the Sierra had a V6 in it, then it will. If it had a V8 in it, then you will have to move the motor mounts and/or purchase motor mounts for the conversion.