This is an amazing write-up. Thank you! I also have the SGA kit and 8hp70 sitting in the garage waiting for install in my 2011 Sport. I'm in about $2500 right now, but still need the driveshaft. I put a stroker motor in the truck last winter and am planning for a supercharger soon. The 545RFE will certainly not hold the power I plan to put down, so the 8 speed swap is a must for me. Your very detailed description (thank you again...) brought to light a few items I hadn't thought about such as the dust cover issue. As stated above, I'm hoping the tuning will be easier with my PCM compared to what you went through. I had Ryan from Flyin' Ryan Performance tune the engine, so I already have HP Tuners. I just have to get the credits for the 8hp70.
Question for you: Who did your driveshaft? My truck is a crew cab, so with this swap I'm estimating the driveshaft to be around 85 inches. I'm being told by most that it will be too long for a 1-piece. Far From Stock is the only place to say it is possible but only with a steel shaft. My 8hp70 is from a 2020 Charger, so I will need to either change the output flange to the truck version or use the Sonnax adapter you described. If I can swap to the truck flange, I think I can use the 2-piece shaft from the newer trucks, but I would rather go 1-piece. Any input would be greatly appreciated.
I'm planning to start the swap in the next few weeks...wish me luck!
I am not sure if the output flanges are interchangeable, but I am assuming they would be. from what I have heard the factory slip shaft (or however they describe the truck driveshafts) are junk. I don't know though. I had a local shop build me the driveshaft, it cost me about 700 bucks which would be 500ish USD. the transmission i am running is also from a 2020 challenger. good thing the guys who buy those cars forget how to drive.
if it were me in your case I would get a two piece shaft made and then just fab up a crossmember for the center bearing, and get a slip joint in the rear half. I have no regrets going with the sonnax adapter and of you are going that route, I have a spare in the garage so pm me if you want to figure something out on it. hasn't been used.
I am amazed that place would build you a one piece driveshaft that is that long. that's an insane length for a one piece shaft, and made of steel too. yikes.