No, not unless you're talking about an iSight model, then maybe, but otherwise they are not showing up as the same part in Apple's parts list for service providers.
There was some old repair program regarding the PSUs in those older iMacs. Don't remember the specifics, since it was a bit before my time, but there was also the bad caps issue that plagued the iMac G5 line, so honestly I wouldn't really advise investing any amount of money into this. It might be the PSU, it might be the MLB, it might be the both of them. This has all the markings of something that will turn into a giant time and money sink on a unit which will have limited utility by today's standards. I'd just walk away at this point. Invest any money you'd spend on repairs on a new unit.
My 20" 2.0 GHz PPC iMac is dead, and I suspect the power supply unit is bad. I found one PSU for sale but it's taken from a 1.8 GHz 17" iMac. Will it work in mine ?