What would you do, 340 Dart?

Here's your options as I see them.

1.Buy a 9" rear. Have it narrowed and perches welded on where they need to be and the axles cut down to fit your A-body.

2. Buy a Chrysler C or B body rear and have it narrowed and perches welded on where they need to be and axles cut to fit your A-body.

Hum... Why don't I see any difference in the amount of work there??? Plus I can't imagine you'd buy a 9" rearend housing cheaper than a Mopar B or C body unless your lucky enough to know where there is one for free. I see B and C rearend housings sell for $50-$100 quite often.

Lastly, as Max said a 8-1/4 Mopar rear will handle 300 hp just fine and they were used in A-bodies a bunch and cost next to nothing most of the time. That'd be my 1st choice for a 300 hp car.

BTW: If you noticed I didn't mention just bolting in a Ford 9" rear it's because it'd be nearly impossible to find one that'll bolt right in. I have messed with a lot of rearends over the past 25+ yrs. and never ran into a Ford 9" that was a bolt in to an A-body. Their not a bad rearend and I'm not knocking them. Just not going to bolt right in to an A-body without a bunch of work.