Too bad she lost interest. As Paul M. posted it depends on what manufacturer produced your kit. I have a “northern” kit made by the now defunct British Coach Works (Pennsylvania). They made VW and Chevette based TD Replicas. All of the body hardware on the BCW cars were OEM or Repro MGTD stuff. Even my tailight lenses are glass. In my opinion the Classic Roadsters and British Coach Works were the highest quality MGTD kits as well as being the closest to the real MGTD in dimensions.
As far as I know, the grille shells are no longer available and rechroming is the only viable option unless you want to pay big $$ to find a good used/unused one (if you can).
As far as your car goes, neither the Chevette or Pinto ever had frames. So, when people say it’s a Chevette or Pinto frame, they are incorrect. These cars were unibody vehicles and had no frames.
All of these FRONT ENGINE/REAR DRIVE TD replica’s are built on a fabricated frames, usually made from mild steel square or rectangle tubing by the manufacturer of the kit or a subcontractor they hire. These are made usually made to accept the donor car’s suspension, drivetrain, gas tank, radiator, brake system, steering column, wiring and as much of the other donor car’s parts as possible.
So, I would venture to say that your MGTD is a Pinto OR a Chevette based kit. It would have either the Pinto or Chevette donor car driveline and suspension. I doubt if it is a mixture of both because of the extreme difference indesign of the drivetrain components. The Chevette used a torque tube drivesahft/rear end with a coil spring and control links. The Pinto/Mustang II used open driveshafts and leaf springs. The suspensions are also quite different. You probably have one or the other, but not both.