Ok so lets really talk K-members here Folks

I don't see upper shock mounts on any of these K-members. I'll assume all use coil-over shocks and the factory upper shock mount. This will require substantial reinforcement of the upper mounts, as they WILL NOT support the weight of the car.

Take a look at the RMS Alterktion.
These are both built for strut cars but they are stock with struts I'm not talking coil over conversions here.

The RMS unit is even pricier then the Mancini unit and requires all kinds of parts to make it work other then just a k-member.

And the response about Mustang/ Camaro demand. I have installed hundreds of Mustang K-members But the 4th gen Camaro k-members I've never even sold one let alone installed one. 4th Gens were shunned buy most for major mods in requards to suspension.