You can get alot of what you are looking for on E-Bay Motors. And they do sell goodmark panels on E-Bay. You can get the motor mounts you are looking for for each application either big block or small block and use the K-member that is in the car. Get a copy of Mopar Performance or a similar magazine and look at the advertisements. They have alot of products for the Challenger now and I guess its because its popular now. As far as drums to discs... its all up to your wallet. They have from stock replacement discs all around to willwood and baer. The stock rear discs I'm talking of use a GM rear disc and an adapter plate to bolt them up. Willwood are offered on E-bay. As far as sheet metal if its in the trunk or on the floor and will be covered why pay more for a product that will be similar and do a great job. But if its going to be seen... fender, quarter panel, trunk lid, hood ect.. then go with goodmark Also as far as trans go big block to big block and small block to small block. They will not interchange like Chevy. If you need any help just post and I'll try to help the best I can. Good luck