...PS -- Pietta does not sell or offer a 44 Spec cylinder.
Good luck with your project.
Yeah, that's why he got the .357 so the cylinder can be rechambered. Who knows, everybody has their own reasons for doing whatever. If 44 Spcl just couldn't be found otherwise, I could see it being more of an option. I would just buy a Cimarron 44 Spcl Model P. However, they chamber that in the Pre-War frame only, so it would be a 3-click gun with a medallion grip. Both of which can be changed, of course. But I'd be more likely to buy the Old Model P in 44-40 and add the 44 spcl cylinder. But I already have enough 44 Spcls, 2 Colts, a conversion, a Thunderer and a '66. Actually, I picked up a used 44-40 cylinder that fits perfectly in my Thunderer so it is dual caliber now also.
Back to the OP, if the barrel on your donor gun is in good shape, you could probably sell it to recoup some of your cost.