Which one do you like? Street use 741 - 742 - 489. Big block 4 speed car probably going to be hard on it. Thanks

742 hands down, no contest. Now if you take a 489 and use a crush sleeve eliminater that’s fine too.

I have used all of those cases without a problem. Even the 741, with the supposedly "small" pinion gear is bigger than a Ford nine inch. The factory used them behind some nasty engines and they held up just fine. Unless you're building a 500 horsepower or stronger motor you should be ok. All of the pinion gears are pretty much the same size where the pinion nut sits.

Being a street car all would likely be fine unless you have your suspension really dialed in with sticky back tires. I would then lean towards the 742 or 489 case

Wouldn't a pinon break at its smallest-weakest point? AND, aren't all the yokes the same.......so what's wrong with a 741? This has been a mystery to me as much as DOT5 Good luck.

i have beat hard on all of the above cases, but since i can's shift a 4 speed for $hit, i'm a wimpy automatic guy.

Yes, the pinion stem ends are pretty much the same but most failures occur because of pinion deflection...IOW, under load, the pinion gear tries to deflect from the ring gear and tooth contact is lost leading to tooth failure. A larger pinion stem and bearing resist this deflection...the 742 (on the right below) has the best combination of stem size and bearing size to resist deflection.

There is a reason the factory went with a Dana behind a stick with a "nasty engine".

That said, the 742 survived just fine behind the warm 413/stick combo in my 64 300 with N50's.

I've crack, (and had some teeth break off) the outer edge of the ring gear teeth on all three rear ends with a 727 and nine inch slicks
Not so on a Dana 60, yet

Well, I gotta say that picture clears it up for me. Great comparison, thanks for that. Once again Mr. Kunkel's expertise teaches me something.

The credit goes to Dr Diff, the photo was pirated from this article in the tech archives.
There is more to the story also.

Go to the tech archives sometime and start reading. That’s where these guys get lots of this stuff from.

http://www.moparts.org/Tech/Archive/axle/1.html

FIXED VERSION;

A serious issue with the 741 is the lack of new gear sets in many different ratios. I have beat on a 741 for years, but if starting from scratch would go 742. Which I eventually did when I went to 4:10