rear suspension lift

another vote for ESPO. I have +1 springs on all my Darts - some of them 20 years old. They do settle in the first year and then more over time, so your best bet is a +1 or even a +2. Be sure to order 6 leaf springs - that's what all the 340 A bodies of your era came with. They come with the front bushings already pressed in. If you want a bit more room get a 3/4 inch inboard kit to snug the front hangers to the frame and uses offset rear shackles. You would have to move the perches on the rear axle in 3/4 of an inch and the kit comes with new perches. since you will already have the springs out it's not that much more work.