For reliability, pretty much stock. Use as much OEM and as few 'rebuilt' or 'remanufactured' or 'go fast' parts as possible. Use local rebuilder who does work him/herself whenever possible.
Modifications:
* The mini-starters are more reliable than the originals. But the originals aren't terrible. Also easy to change out. call this Optional.
* Alternator. Original will do fine unless the car will be running air conditioning, or idling a lot a night with lights & wipers on. A 'squareback' will handle that. Options will depend on load.
* Leave the ammeter alone. Its useful. Since you're in a humid climate, a parallel wire direct from the alternator output to the ammeter's altenrator side would add reliability. You could do the same from the fusible link to the ammeter's battery side. (aka Nacho's parallel bulkhead bypass).
* MSD distributor. NO. Not necessarily more reliable and the distributor will have a less efficient timing curve. Stock distributor is plenty reliable. Only issue with points is they do wear, the cam wears, and therefore they need regular maint. Good points and condensors are getting harder find (see Halifaxhops for good ones if none local). If that fails the 'reliability' requirement (and I can understand that) then go for a Chrysler built magnetic pickup version with correct advance.
* MSD ignition. The reliablility has varied over the years and there's really no need or advantage to a multi-spark CD ignition on stock engine. OTH it can be triggered by the points distibutor. Other options are Pertronix Ignitor I into the points distributor (check if that's doable), or an externally mounted genuine HEI module with a magnetic pickup distributor. Whatever is purchased, have a spare on hand.
* FI. No. More stuff to go wrong. Requires a new wiring strategy. All this to do what a carb does fine. If there was a ton of emmissions controls, then EFI can have an edge, but not for a '69.
Great engines.
