The FJM spindle is .375 taller and these ball joints are offered in .5 and 1.0, so they are going to alter geometry. Whether or not you need the change in roll center and the additional camber gain will depend on your overall combo. Things like ride height, spring rates, body roll, tire diameter, rim diameter, etc will all factor into whether or not these actually improve things for you. If your car is significantly lowered, these may help. If you have soft spring rates with small sway bars that allow a fair amount of body roll, the camber gain may be of assistance with keeping the tire flatter.

Remember these parts are developed for oval track racers that may carry around a half dozen different control arms to tune for specific track conditions, especially in the dirt. Its entirely possibly that these are for use with geometry that will never be found in a stock based pick up point suspension like what we have under our cars. The radical camber gain a 1" over stock ball joint would provide is likely for use on a dirt track where a lot of body roll is needed for bite and you need a lot of camber gain to keep the tire face in contact with the track.

Now, if you want to understand if these can be used, you need to map out your pick up points and graphically see how they change things. This can be done with pencil and paper, but it requires A LOT of paper to actually see the incremental changes .375 and .5 can make over the stock locations because the changes become very minor, where you probably can't see them without using a gauge. It obviously is easier to use a program that can map and graph these all for you automatically and then demo changes in dynamic sequences as well. I know Steve Smith Autosports Publishing has a program that is around $100. I'm sure there are other out there in addition to the the Performance Trends piece jcc referenced.

Just taking a swag at it, the .5 unit may help but I doubt the 1.0 unit would really help. I typically lower my cars to a point where the lower control arm pivot and lower ball joint are level. This is considered very low for a street going Mopar but it matches well with my tire diameters. This drops the front roll center 2" underground. Changing to the .375 taller spindle brings this point back up to 2" above ground. Adding another .125 of height may bring that roll center up to 4" above ground, which may not be too bad.

I may try to model it sometime in the future, but I also need to go back and reconfirm all my set up measurements. Accuracy of finding these is HUGE to the overall results but it is also very difficult to get accurately in a stock layout with a tape measure and nailing these down will require I spend time with a plumb bob and a layout sheet underneath the car.