I use this one now, but it may be a bit pricey to just see what a spindle change does. They also have books that outline how to perform the analysis manually using plot points and paper. I used method this when I was racing ovals back in the 1990s. You just need to use a large, like 5-6 pieces taped together, to get any meaningful detail in the plots.
https://www.ssapubl.com/product.aspx?nbr=C249What spindles are you swapping to? If you a changing the stock E body units for the taller F body units, the biggest change you will experience will be a raising of the roll center height.
Where are you guys getting your chassis pickup point locations?
You just have to go out and measure them. They will differ from car to car based on ride height and tire aspect ratios in use. I typically run my cars so low my lower control arm is horizontal to the ground which has a big impact on the geometry compared to a car set at a stock ride height.