The crank carrier holds the crankshaft central in the crankcases and I'm not sure modifying something this critical without lots of research and development is a good idea and does it rob the bearings of some oil pressure?
I'm guessing the Ladder Casting Modification on the invoice is the crank carrier mod?? Would like to know what they did, nothing at all on Google?
Also why was it rebuilt, sounds like the only work was to carry out this modification, very strange?
I'm also curious why they charged for, 2x crankcase half gaskets (as there is no such thing) and also charged for Loctite 5900 as this is the sealant that does the sealing of the crankcases? Could they mean coolant channel seals?