Rear end options.

Hey all, here is my dilemma.
I have a 1974 Duster with a hopped up 360 pushing around 375-385hp range at the crank.
With a A999 transmission converted to non-lockup with a cheetah valvebody.
I currently have an 8 1/4 suregrip rear that is well worn and noisy. I changed out all the bearings but come to find out I think the clutch in the carrier is giving too much, it almost acts like an open diff. It has about 200,000 miles on it.

I stalked a local salvage yard that specializes in classic cars.
I've done some research regarding Chryco 8 3/4 rears and Ford 9 inch. I know I need 43 inches for the perches.

I found some B-body and one early A-body 8 3/4 axle. All the spring perches measured 44 inches.

I found a few ford 9 inch axles as well. A few of them measured 43 inches at the perches. One out of a 60's mustang, a few falcons and a I think a comet.
He wants $300 for either the 9 inch or 8 3/4 axles complete. I want keep the process as simple and budget minded as possible (under $800)

Now the question is do I go for the 9 inch, 8 3/4, find a new or (if possible) rebuild the 8 1/4 carrier.
Open to other options as well.

And another thing, all the rear-ends in the salvage yard are one-leggers. There were no sure-grips or trak-loks or whatever.

*Edit: I did find one chrysler (300?) car that looked like it had a Dana 60 one-legger.