I'm not sure there's a specific reason why you want to narrow an A body housing, but wouldn't it be cheaper too narrow a B, C, or E body housing and then sell the stock length A body housing to someone who could use it?
Don't see someone making any money with the current rusted condition of the housing.
Just cut out the 3" and have the ends rewelded back on on a jig.
For $125 I know what I would do.
