Need an ignition controller for a 6.1. MSD only list for 5.7 and the fast unit is more for EFI than carb. What are you guys using? I believe just changing the reluctor wheel would alow the msd to work on the 6.1. Has anybody tried to change them? Any problems?

The FAST unit in stand-alone mode works fine with a carb.
Done several.

The Hemi 6 controller from MSD can work both 5.7 and 6.1. There is a jumper loop in the harness that you either leave in tact or cut, depending on engine. The instructions are available on line from MSD. I know this works for a fact. I am running a Hemi 6 controller in a 5.7 right now that was previously used on a twin turbo 6.1 Jeep.

I run a late 5.7 MSD controller on my 2010 6.1 crate motor.

The only thing not compatible was the crank and cam sensor plugs - so I changed the sensors to 5.7 ones.

Works perfectly.

I'm here scratching my head wondering what the difference is between a 5.7 & 6.1 than cu. in. ?? the connections?

Yes it is pretty much just the connections as far as hooking up the MSD..

The coil connectors are different, but the hidden difference between the early 5.7 and the 6.1 is the crankshaft tone wheel. That is why the loop wire on the harness has to be either cut or intact, depending on which tone wheel is being used. The later 5.7's ( with same coil setup as 6.1 ) use the same tone wheel as the 6.1. That being said, I don't know what kind of tone wheel is used on the 6.4 or the 6.2 Hellcat engine.

Like I said...I used the later 5.7 harness on my 6.1

The only issue was the crank and cam sensor clips - everything else was plug and play

All 5.7 from 08 and down and all 6.1 have the same reluctor wheel. (Toner Wheel)32 teeth IIRC
The only difference in the two are the 5.7 has three bolts holding it on the crank and 6.1 has 4 bolts.
All 09 and up 5.7 6.4 and 6.2 have a reluctor wheel with 64 teeth. I know the 6.4 has 4 bolts holding it to the crank. I'm assuming the rest have the same.
I BELIEVE the only difference in the MSD wiring harness has to do with the early 5.7 with the crossover ignition wire and the 06 and up coil on plug wire. If you have the early version of 5.7 you can easily convert it to the later version.
So long story short buy the later version and convert if you need too.
Matt