Help needed on buying a gen 3 Hemi motor

I'm getting ready to get my feet wet on Gen 3 hemi motors, probably a 6.4 out of a wreck or burnt up pick up. I've owned and race both gen 1 and Gen 2, no gen 3 yet.
I'm planning on putting the motor and trans. in a 1967 Plymouth Satellite with the stock EFI setup and auto trans starting later this year or early next year depending on how and when I find the parts, I have no real world hands on experience yet with EFI and computer control tranny. this is a going to be a learning experience so all help is appreciated
Is the 8 speed auto tranny the best choice for this project? If not which one would you choose, I have a clean slate so all options are on the table How do I identify the motors and tranny to make sure I get what I'm trying to buy?
What are the years to look for and buy the 6.4 motors and 8 speed trannys ?
Is it best to try and use the stock wiring harnesses and controller or buy and use custom after market parts?
Thanks in advance for all the help your offering!

I know that the stock 6.4 uses only ONE narrow band o2 sensor, that makes it useless in my opinion, Holley has a good wide band set up for the gen 3 hemi

I have a innovate LM1 converted to their LC1 dual sensor kit, I don't think I can make it work with the stock stuff for that later system, can I?
I appreciate your help on this

No, not with the OEM computer set up, I would use the Holley system, it has fuel management from the wide band o2 at ALL throttle positions ie. closed loop, the factory set up on the 6.4 goes into open loop under a load & also at WOT no fuel management at all, just runs off of a base map, the Hell cat uses wide band o2 with closed loop fuel control & adds more or less fuel to keep it in the correct AFR.

I think the 8 speed is the way to go. It is going in my barracuda right now but it is behind my warmed up original 318. Sound German Automotive has the controller and he is a great person to deal with. I've asked him (Russell) many questions over the years and he has always responded. I haven't even bought the controller from him yet too.

In my hellcat swap im running the Mopar crate controller. The mopar crate controllers are very nice for all the swaps. High quality , comes with everything ( gas pedal, body control module etc) and the PCM is unlocked so it can be tuned without unlocking it. Im running a Cope 727 for a trans. My current project is a 99 Dakota RT that I will probably go with a nice cammed 6.4 and an 8 speed. They didnt have the 8 speed really proven when I did my hellcat swap. If you get a used 6.4, make sure its a motor that didnt eat a lifter.

The mopar crate controller for the 6.4 has one narrow band o2 sensor, the HC has the wide band set up.

I absolutely hate all the shifting these new fangled trannys do! 8 gears is about twice what they need. These modern engines are made to make more TQ over a far broader range of RPM and they can E A S I L Y make enough TQ to work with a 4 speed auto from zero to 200 MPH with appropriate ratios.

And to keep things as simple as possible, I would run a good ol 727 with a GV overdrive. Or the most "new trans tech" I would get is a 518 trans...lol

I like the 518, it is even simpler than GV and has a taller (more effective) OD ratio. It is just a 727 with a very simple and effective OD unit. Of course I like the a-500 even better because they are lighter, less drag, better 1st and 2nd ratios...

Remember if you decide to use a 727/518/46RH trans, you either need to run a manual valve body, or figure out trans linkage for the 1-2 and 2-3 shift. Only the 3-4 shift is hydraulic on the 518/46RH and electronic on the 46RE. Bouchillon has an adapter kit for the throttle pressure linkage. This takes care of the 1-2 and 2-3 shift. In my opinion, if you run a modern engine, put a modern trans behind it.

I built a 727 for my Road Runner. Trans break, rmvb. Mine is a 6.1 with a Procharger.

Very happy with a 518 behind my 5.7, runs great, put together a completely automatic controller for the OD/LU.
Had a RMVB with my old 340, that got old after awhile.

I'm building a replacement 5.7 for my 2007 truck. The original engine will be saved for a future build.
I may use the original 5.7 in my other '70 Charger using a 500 or 518. I'll have durability with an overdrive and lockup converter. The .69 overdrive ratio is great compared to the other options out there.
If I recall, the A-500 was used in many vans. You know THOSE were not lightweight. The 2.74 and 1.74 1st and 2nd ratios are better than the 518/727.