Is there any other rear that will work in my '65 barracuda??????

To me, it Really sounds like;
you would be better to sell the 6 cyl car, and buy one thats already a V8.

As much works as is involved with the Early Abody
with putting a V8 engine in, I doubt I will ever do another V8 engine swap.

Doing a conversion /6 to V8 has to be Much more work. :(

Don't forget the Early Abody you either need to buy some Spitfire headers,
or the 1964-66 273 Drivers side specific exhaust manifolds, the passenger side one most any year will work.

You need the V8 style, dropped steering center link.

Does your car have power steering? That may add another set of conversion hassles, {hoses brackets etc.}.

You will need the shorter 65-66 V8 radiator.{Shorter than 67-76}

You should really change the front torsion bars to the V8 rated ones,
and I suggest you convert to 14inch tires and rims.You might appreciate the tires holding more weight, when you add weight to the car.
I am using 205/70/r14's on my car.

The factory V8 cars in 1964 came with 7.00x13 tall tires,
the 65-66 had an option of 14"s.

I went to the small "Dakota" style starter, when I swapped the 318 in for the worn out 273; they weigh less, use less power
and allow more room for the exhaust and steering components etc.

Lots to consider. Think it over and research the work involved.
Take any time estimate you have, of doing this work and multiply it x 2. :)