This is what I found with these center sections. It goes in this order this is just for the 8 3/4 rears. 742 is the strongest because the pinion shaft is very large and the same size to the splines no taper it uses 2 large bearings and it uses shims not a crush collar. 741 pinion shaft is smaller then 742 same setup. The 489 uses a crush collar and pinion shaft is tapered small bearing on the yoke side big bearing gear side. They will all interchange in the housing you have not sure about axles. They are all strong and they are all great dont get me wrong but if you use a 489 and you are drag racing make sure you use a sleeve with shims instead of the crush collar. Especially with a stick car. One more thing the 489 I think you can get parts easyer and cheaper they are more available i think they are cheaper to buy as a whole assembly too.
I guess its all preference too.
-------- Original message --------
From: Ray Bell <raybell46@xxxxxxxxx>
Date: 6/16/19 4:27 AM (GMT-06:00)
To: The 1962 to 1965 Mopar Mail List Clubhouse <1962to1965mopars@xxxxxxxxxxxxxxxx>
Subject: Re: Rear end replacement for a 2070141
Even though it's a B-body, the rear axle in that model is wider than the later flanged B-body axles. Very close to the same as C-body axles if I recall correctly.
The C-body rears are the easiest of all to find and, if complete, come with bigger rear brakes. The 741 centre section is not a weakness at all, nor is it typically for A-bodies with smaller engines. Virtually every C-body sold in Australia, for instance, came with a 741. The gears are just as strong, the only down-sized component is the front bearing on the pinion shaft.
I think the advice you've been give, run it and see how it goes, is good advice. Spend your time and money on things which will make a tangible difference.