I forget the 73 had that Iso spring deal here are the parts you need to remove that:

http://www.firmfeel.com/Isodeletekit_b73up.htm

Or just get all the parts used off of a 72 or 71 B body and your good to go.

And these hangars with the shorter length for the stock 22" front segment spring with the 2 different height holes for the front spring eye.
Will get that large B body closer to the ground.
Lower CG = better handling.......

http://www.firmfeel.com/leafhang_b.htm

Then after you get rid of that your rear springs will be exactly like on my 72 and I have not bent my new bought this year Made in Mexico XHD springs yet or build your own......those should not bend