Where do I get 160 pound per inch leaf springs?

[HP2]

Check with Detroit/Eaton spring.

Landrum makes 150# and 175# off the shelf springs. They could  most likely make a 160# for a fee. Afco makes a 166# mopar springs off the shelf.  However, both of these company's springs are based on the mopar  oval track springs, which are slightly different than stock. The front segment is 20  1/2" compared to the stock 22" and the SS springs 20". So you will have to use an SS front hanger and either a) accept your rear axle will be pushed back 1/2" or b) weld up the mounting hole in the SS hanger and relocate 1/2" forward.