I not very good at write ups so bare with me. The only real modification you need to do to make these lower controls work is drilling out the bolt hole bigger. Heres a link to the lca i used https://www.americanmuscle.com/jm-adjustable-lower-control-arms-blk-0514.html I was able to get away (but do not recommend) with just drilling 1/2inch holes and using 1/2inch bolts, but the correct size bolt that should be used is 14mm.
The mustang lca have a wide side and a narrow side, so me not know if it makes a difference i just put the wide side to the rear end and the narrow side to the frame. Its a pretty tight fit but i just took a mallet to it and it went in.
The narrow side will need spacers, i just found some lieing around. The spacers added about 3/8 of an inch but i feel like for a tighter fit id go 1/2inch
I hope this make sence, does make it easy to adjust the pinion angle