If I was racing a CP Mustang, I would do what Brett Madsen is doing. Run the MM k-member, take the absurd 10% weight penalty, bitch slap everyone else in the class (hopefully) and take home the trophy.
To clarify, the k-member has four holes on each side, numbered 1 through 4 from front to back.
If you use rubber FCA bushings you can get away with a lot in terms of hole placement since the rubber bushings don't have thrust surfaces that need to be parallel with the four k-member tabs. Only the end of the crush sleeve needs to be perpendicular to the tabs. Once the bolts are tightened, the sleeves will bend this small area of each tab into conformance.
As soon as you use polyurethane or Delrin bushings, things get much more complicated. The bushing is the thrust surface for the k-member tab. They must be parallel or you will get bind and/or lots of play. To properly relocate the holes TO ANY DEGREE it is a ton of work to do it properly when using a nonrubber bushing.
Assuming the car doesn't have ABS, I would keep the stock antidive angle. Note that as the car is lowered, the amount of antidive will increase even with the same FCA angle. If the car has ABS, you can get away with a little more antidive, but Ford already built this into the 1996-2004 k-members.
I would raise all four holes the same amount. The limit on how high you can raise the holes is going to be based on the OD of your bushing package, and how much work you are willing to do to the k-member to get the matching FLAT thrust area raised also. Holes #2 and #3 are easy because this entire pocket is just cut off and moved up. Hole #1 can be moved upwards quite a lot. Hole #4 limits everything since the metal on the back of the k-member curves up and forward just above the stock hole. To move this hole up very much, you are going to need to cut out metal on the chassis and install the rear FCA nut above the k-member mounting plane.
Once I installed some Delrin bushings into stock FCAs that went into a Griggs modified stock k-member. There was no way that the very rear thrust bushing was ever going to be able to rotate against the rear thrust surface of the k-member due to the curvature of the metal noted above. I ended up machining and grinding my own rear thrust bushing to match the curvature of the k-member metal. This kept the rear thrust bushing from rotating and forced the sliding surface to be between the front of this thrust bushing and the aluminum case pressed into the FCA. I had to grind every thrust bushing in the FCAs at an angle to give both FCAs nice parallel sliding surfaces. I had the k-member, FCAs, bushings on a workbench with air tools and this took about 8 hours to do. Have fun. When I was done, I could spin the FCA nuts on and off the bolts with my fingers.
For every inch you lower the car, you need to approximately raise the FCA pivot 1". You very quickly run into needing to move the FCA upwards far more than it can physically be moved due to the hole location limitation. Sometime during your 25th hour of grinding, cutting and bending, you are going to realize that it will be much faster to fill out the SCCA paperwork to request a rules change and then just purchase a complete k-member, than it is to pick all of the steel slivers out of your fingers and finish this project
The other consideration is bumpsteer. For ever inch you raise the FCA pivot, you need to lower the outer tie rod pivot 1". If you are going to use 16" wheels, forget it, your car is going to have massive, uncorrectable roll understeer. I know of several competitive CP cars setup this way, but they also have lockers in the rear, so probably the two screwed up things counteract each other and make the car driveable
I would run 18" wheels and as tall a tire as I could get away with.