Picked up my H190 320 pickup rearend this morning. I think this differential should do the the trick. It is actually 44 inches wide (48 inches drum to drum). The axles at the splines are 29mm in diameter compared to 22mm on the H165 axle. The axle has 13 splines instead of 28 like I thought it would have. The splines are deeply cut into the axle. Center Diff ratio is 4.875 which should scoot me down the track pretty quick. No more crossing the finish line in 2nd gear, I will have to shift. It's a 6 lug but with 1 inch adapter plates, it should put my 4 lug wheels, right where I need them.
Will post pictures on Project Build page shortly.

More good news. My girlfriend's girlfriend's husband owns a machine shops and he said he would fab me some 6 lug to 4 lug adapter plate. The axle is 42 inches so 2 inch adapter plates should make up the difference depending on the width of the drums. May not have to move my leaf springs.

OK.
Next week I'm picking up a rearend out of a 320 pickup. 6 Lug with (I'm assuming) 4.80 gears. 42 inches across from brake plate to brake . Should allow for wider tires. Leaf Springs will have to be moved in and lugs redrilled. If anyone has more info for me, let me know. Thanks.

Anyways....
The roadster rearend is for sale. Two Franklin's and you can take it home. Got an eyeball on a H190 pickup rearend. Thanks Bart!

You can do some rough calcs, the strength of the axel (assuming the same material and design) is related to the cube of diameter, so guessing at about 20mm diameter for the one you broke, the new one will be ((20+2)/20)^3 times stronger. The engine will be making nearly twice as much torque? Twice the strength means the axel needs to be 1.26 times bigger in diameter, or 26% bigger.

Might help if you're good on a calculator.

Yes, we got the Vanette -- though few people can remember. It was recalled and destroyed within a few years.

Don't go near a 9" Ernie.
I've read numorous stories of guys who's cars have gone slower after an upgrade to 9" due to the greater driveline losses from the bigger heavier diff gears etc.
Just find a decent H190, and give it death! Even a diff from a 240/260C etc would be good. The Vannettes (Which I'm not sure you got in the US) had a nice lightweight Aluminium center housing.

Not sure of today's price, but yeah 10 years ago...

Are you saying, you get the axles with the housing but not the center for $450? Are you sure about that?

Narrowed Ford 9" is $450. Throw in a junkyard center and it is unbreakable.