741 open to 489 suregrip swap

Make sure you have addressed the thrust block depending on which type of axle bearings you have

He did not say if the 323 unit was a sure grip or open unit. The thrust block is only an issue with rear housings that have been converted to green bearings and center sections running the "old style" clutch style sure grip unit. On the old style clutch type sure grips, there is a thrust block to assure that the axle end play adjustment can be achieved. They tend to fall out of the unit when the center section is removed. The block HAS to be there if you are running the stock adjuster and does not have to be there with green bearings. On newer sure grips and open units it does not fall out so the issue is moot.

I very highly doubt that a 67 Satellite with a 741 case 276 open would have been converted to run green bearings so this is probably something that you don't have to worry about.