A lot of the lye calculators have an option for shortening, or "hydrogenated vegetable fat", or simply crisco (note that you want
new crisco, and not old crisco, the formulation has changed due to health reasons). MOST shortenings in the US are palm and soybean oil (google is your friend, and has lots of answers

). Just use that option when you use shortening, do NOT use the lard selection! This is for actual lard (pig fat) and has a completely different SAP value.
I have used both types of fats in my soaps. I prefer lard over shortening. But it is all personal preference. Just make sure that you run every recipe through a lye calculator, especially ones found online! Its amazing how many of these are very lye heavy.