Springs from a 720 are almost exactly the same dimensions as the first and second gen rears. Your rears are
22x29 1/2" center pin to ends and the nissan are 22 1/2x 25". My old nissan flexed pretty decent and hauled a lot of weight with ease. Worth checking into, I dont recall if they have the nylon pads or not but they are the same width as toyota.
![Wink ;)](https://board.marlincrawler.com/Smileys/marlin/wink.gif)