Going rate?
The usual 489 COMPLETE center sections seem to be priced from 500 and up when I trudge through the Mopar Nats and Carlisle. Best deal I ever got was $85 for a complete 3.23 489 SG in the last century. Saw it, bought it, no brainer. It's in my 68.
Ok, just because I'm bored witb this stay at home thing and really should get back to rebuilding my 1964 heater.
The 489 cone style became standard in A bodies starting in the 1969 model year. I have 2 1969 abody 8-3/4 rear ends and both are 489. One is a factory 3.91 SG that came in my 69 A56. The other is a 3.55 SG.
For Matt, the crush sleeve can be eliminated with a crush sleeve eliminator kit.
Technically the 489 is strongest because it has a larger nicely tapered 1-7/8" diameter pinion. Compare this to the smaller 1-3/4" stepped pinion in the 742. (stress riser) 741's are the weakest. Ehrenberg makes a case that a 489 is stronger than a Ford 9".
Really I'd probably prefer a 742 cause they are rebuildable clutch type, not wearable cones.