1970 Duster base model slant 6 rear differential 2070051 spider kit

And that mustang/falcon 8 inch ford is a much more durable rear axle, too. Several people on the those forums running upwards of 450-500 hp with them before having to go to a 9 inch. But the five lug is usually harder to find and pricier than the four lug, too. The four lug straight six units were fairly affordable the last time I checked, but I cringe at running wheel adapters on anything larger than a cheap lawn tractor.