Fan shroud: '70-'71 swap into '73?

abodyjoe has it right.

Also, what is the part # that appears on the shroud? The part number can be referenced against the '71-'72 parts manual, and then you will know which cars / radiators the shroud works with.

If the shroud is for a V-8 factory car, or a V-8 car with factory A/C, each will have different applications.

If the shroud is for a 1971-72 V-8 car with A/C, or a factory 340 car, if the shroud does not fit your application, you should sell the shroud, assuming it's in very good (not broken, cracked or missing pieces) condition. I'd be interested in a 340 shroud for a factory 340 car I have without a shroud.

Look at the bottom of the shroud for a part # and go from there.