The shuttle is stock, and with the nuclear engine payload it can get ~18 tons to the mun and back plus 8 kerbals.

Launch (the launch pad is the only modded part in the shuttle build)

https://preview.redd.it/nocyeziz2jxh1.jpeg?width=2560&format=pjpg&auto=webp&s=251372af3190b10f20d358118339444b841ecb23

Nuclear engine deployment and Mun Transfer Burn. Takes a few orbits to get the AP to a Mun intercept)

Mun capture burn

Capture burn complete, phasing to align with the base near the south pole

Phasing complete, moving the lander into docking orientation for crew transfer

Crew transfer to lander

Lander arrives near the mun base. Only 1 hab has landed thus far, with the next module arriving during this sortie.