Good work, I may have to do that myself here soon. I'm thinking the same as you; there couldn't be much harm in some careful sealant application, right? It would need to be a very thin, carefully applied sealant, for sure. I think you're also right about gaskets messing with the impeller tolerances.
What I'm wondering about is the material those thin plates are made out of. Is that bronze or something? Is that supposed to be the "seal"? Is there a chance that the original design counted on those being softer than the end caps so that they complied with the machined surfaces of the housing/caps?
