I set out to build an exploration Mandalay with at least 80LY jump range (with a full fuel tank) that didn't compromise on the what I want to use it for. This is the build on edsy for my ship, Elize
To achieve this build requires engineering almost every aspect of the ship, and access to the Guardian FSD Booster. These are the modules I chose, and their reasons.
Hardpoints
none - this is an explorer
Core Modules
1C Lightweight Alloy
This is the default lightweight armour. I've engineered it to grade 5 Heavy Duty with Deep Plating. This adds a significant extra hull strength and adds no extra weight, so doesn't hurt jump range.
2A Power Plant
I engineered this with grade 5 Overcharged with Thermal Spread. Normally, Overcharged is not a great choice on an exploration ship because of the added heat but the Mandalay runs so cool that it can run Overcharged and still won't hit over 58% heat even with SCO engaged. I put Thermal Spread on because it helps mitigate some of the Overcharged heat - but actually you can throw Monstered on it instead if you need extra power and it still won't come close to overheating.
4D Thrusters
These are the lightest thrusters it can use, and I engineered them with Dirty Tuning to grade 5 with Drag Drives experimental effect. This just gives it some extra speed - it'll hit over 340m/s at full speed and just touch 500m/s when boosting - more than enough for an explorer.
5A Frame Shift Drive (SCO)
Engineered with Increased Range to grade 5 with Mass Manager experimental effect. This provies maximum jump range.
4D Life Support
Engineered with grade 5 Lightweight to maximize jump range
3D Power Distributor
Engineered with grade 5 Engine Focus with Cluster Capacitors. As an explorer, I don't need perma-boost - I only really use it to get away from stations or planets after landing. Over the years, I've found a ship capable of 2 boosts in succession meets my needs. This Distributor gives me 2 boosts with around an extra half second delay between them, which is fine.
5D Sensors
Engineered with grade 5 Lightweight to maximize jump range
5C Fuel Tank
The standard fuel tank, no reason to downsize.
Utility Mounts
none - but if you prefer even stronger shields, a 0E Shield Booster with grade 5 Heavy Duty + Super Capacitors could be used here.
Optional Modules
6A Fuel Scoop
I have no time for slow scooping ships. This is the best scoop available for the Mandalay.
5H Guardian Frame Shift Drive Booster
The biggest Guardian booster available, a fixed 10.5 LY on jump range
4D Shield Generator
Engineered with grade 5 Reinforced and Hi-Cap experimental. There's no point in fast recharge for explorers, and resistances make no difference to a bad landing. There's also no point going for paper shields - your biggest enemy is gravity and you should be prepared for it. You want the most powerful shields that protect your ship for the least amount of weight. These will protect the ship in a full speed impact, and even when boosting at 500m/s the ship will survive - in my tests, the shields would be wiped out at 500m/s with just 1-2% damage to hull (assuming 4 pips to shields). Seeing as I tend to avoid boosting full speed at the floor these are more than adequate. You could add an engineered Shield Booster in Utility Mounts for even more protection but I'm happy with the protection provided by these.
4A Auto Field-Maintenance Unit
Gives the ability to repair the SCO drive after extended neutron boosting. Powered down until actually required.
2G Planetary Vehicle Hanger
While you can do exobiology in the Mandalay without an SRV, I do like a drive about on planet surfaces so the SRV hangar is a must for me.
1E Supercruise Assist
I actually don't use this. I had a free slot, it weights nothing, and a lot of people like the SCA so I installed it. It feels even more redundant in my ship since SCO, when journeys that took minutes or even tens of minutes are now over in seconds.
1E Advanced Docking Computer
I love a docking computer. Great for when you've been out exploring for months and the muscle memory for landing hasn't quite kicked in. Weighs nothing so doesn't affect jump range.
1I Detailed Surface Scanner
This is the pre-engineered DSS available from human tech brokers, providing +40% probe radius. Makes mapping trivially easy.
At this point, I had everything I needed but still had 2 slots left. I added these:
3A Auto Field-Maintenance Unit
3A Auto Field-Maintenance Unit
As per the 4A AFMU, these will help keep the ship repaired when neutron boosting. They will also be left off until actually repairing. Having multiple AFMUs on a ship speeds up repairs. They weigh nothing so do not affect jump range.
And that's it complete. She jumps ~81.2LY on a full tank, and just about 88LY on fumes.