Would there be any problems booting a recovered computer with a HDD from an old iMac? Sata cables etc. match, asking about software issues rather.
Unless it still has Mac OS X installed on it, it should be identical to modern day hardware in terms of storage devices, depending on age of the machine. Apple doesn't necessarily get that proprietary. But, unless it will be on that identical iMac, it will not boot, Apple does this by building into the EFI the machines board ID which is typically a generic number across all models of that specific iMac than maybe a Mac Pro that will have a different board ID. Essentially, no you will not boot it's OS or what not unless it's completely reformatted or put with an identical iMac model.