I don't have the Space Shuttle Discovery from Lego so I printed one and changed the floor that it fits perfectly, therefore this remix. For connecting you'll still need a Lego pin. The nose still needs support. I have also made a mount that fits the base of the paid model since the original mount is part of the lego set.
Bought the SRB and External tank on Cults3d: https://cults3d.com/en/3d-model/home/solid-rocket-boosters-external-tank-for-lego-10283-nasa-space-shuttle-discovery
The author remixed this model.
Changes to the floor of the shuttle, To connect to the SRB and external tank there are still Lego pins needed.