Ahh, a project of passion. Excellent! So if I read this correctly you have an affinity for the K5 Blazer, and also feel the Cummins is the ideal power plant.
So, why not go with a 24Volt Cummins? With either inline power plant option you have plenty of room on the sides to hang dual alts. May require some fabrication work for the mounts but you would keep the wiring pretty much stock for the CUCV.
Sorry if this is a crazy idea.
As for me, I am planning on sticking with the GM options for a lot of the positive reasons stated above. I have a really good friend who is a serious MOPAR nut and who thinks I am crazy for sticking with the GM's. But he still can't believe that my two CUCV's are daily driven and are just as reliable as my Honda's. Get in, turn the key, (wait for the diesels of course) and go!
When I began to wrench on these years ago, I had forgotten how well built and in some cases over built these vehicles were. In an era where built in obsolescence was king and people were trading their cars in every three years GM still understood that especially for trucks certain parts should be repairable with replaceable wear components etc. It was fun to tear down and repair an alternator again and not just throw in a new one and toss the old as is often the case on modern cars. Even the steering column is completely rebuild-able.
I have added a Gear Vendors to the M1008. It now is driveable on the highway. I am adding a turbo to both. I am adding A/C to both. I will need to fabricate a mount for the compressor. As I will never need the extra capacity of the big rig batteries (and modern AGM's are darn close anyway) I reverted the battery mounts to the dual civilian style and made custom 1 gauge cables for the battery's. Ran the crossover cable over the radiator so the "front" battery is on the drivers side. Ran the 12v positive feed up the drivers side through a 150A circuit breaker and over to the junction block and got rid of the fuseable link. I installed a civilian style overflow on the passenger side fender well. The trucks are tons easier to work on especially on the passenger side with all the extra room. The tranny is bulletproof and easy to swap/repair. They are low complexity mechanically driven and CHEAP to repair. They are a BLAST to drive and my kids and students absolutely love to see and ride in them. I am very pleased with the way they have turned out, and don't believe I am done enhancing them yet.
Lastly, I have an easy and "cheap" engine swap if I need it with an optimizer or P400. I could not replace these old school trucks with their "charm" for anywhere close to the $8K an engine would cost with a "modern" truck.
And really lastly, I get 18+ MPG in dead simple machines.