First, none of the big name kits like HDK,RMS or Gerst are "Pinto suspensions" stuffed into a mopar chassis. I know the only thing they share are the base spindle design. Some like the Gerst are using redesigned/improved mustang II forged spindles. But other than being a spindle that has been redesigned to take care of some of the issues with the mustang II factory spindle, there is no other similarities to that of a mustang ii or the pinto for that matter. Lots of cars use a coil over design, pinto's are not unique to this. The geometry of these kits are totally different, materials are different etc. It's not simply cutting the suspension from a Pinto and putting into a Mopar.
As for your weight savings thing, you've got some valid points there. And I will agree, a properly tuned suspension will almost always outperform an untuned one. The aftermarket now a days has grown to where mopar owners can tune torsion bars quite well.
we've had this debate before, we'll have it again.