Yes they do.
YES there the same.
Not sure what the buck is on a Chevy pickup, need more info.
If they are the same engine, it's highly likely the trans will be the same .
same place it is on every car on the bottom of the radiator
No a 1972 Chevy pickup is not the same model as a 1973 Chevy pickup. I believe it goes from 1967-1972, 1973-1980, 1981-1987. Doors will work from 1973-1976, 1977-1987. You would need to find 1972 doors as they are the only ones taht will fit a 1972. 1967-1971 are the same but there is something different about 1972 doors.
in a full-size YES! you will need new motor mounts, fan shrouds, possibly starter and flywheel, radiator, either conversion to carb or a motor from a similar year 1500 and the computer but the harness should be the same.
If the Chevy Celebrity radiator is smaller that the Saturn radiator it might well overheat from not enough cooling capacity. If the Chevy Celebrity radiator is the same size or larger than the Saturn radiator I would think it would not over heat.
If the tires are the same size, they will but the rims won't.
YES, They are the same engines. That would be a direct bolt in.
Yes. '99-'01 same
YES, All the cabs are the same from 1988 to 1999
No it's not.