Try the following site: http://magister-plasticum.com/
3D printed masters and resin cast product. They are out of Portugal, but I ordered the '77 & '78 Plymouth grill and headlights and was pleasantly surprised by both the overall quality and the quick delivery time. You can order the '75 & '76 single round headlights and finagle the '77 grill to add the parking lights, etc. (or find a builder '75 Roadrunner and steal the grill). Much better than what is posted above.
As mentioned earlier, I know Missing Link offered a '76 Plymouth Fury 4 door trans kit at one time (I have one); you might want to PM him through this forum and see if he still offers the kit, or perhaps the grill and lights.