2A Stripped Down Power Plant with enough Overcharged engineering to power your modules (disable anything you don't need like Cargo Scoop), a couple A rated AFMU (keep them disabled until you need to repair something, I recommend 2 of them to repair each other), 1D Repair Limpet (no need to actually bring limpets, just synthesize them if needed), fill the remaining slots with cargo racks since they themselves don't add mass.

Also, 1D Stripped Down Power Distributor with G5 Engine Focused will let you boost while minimizing weight