Given that they are all from DELL they can have a couple different configuration options.
Without knowing the exact configurations, I can't guarantee anything.
If the GX270s were heavily used, there could be quite a bit of aging on the PSU capacitors which could prevent the gx270 PSUs from delivering enough power to the gx620.
That being said, there is quite a good chance they will be good enough and I don't see any good reason not to try.