I figured out the balancer and the flexplate wanted for this build, and they are on the way now. Of course with any build its all the small things that start to add up including my slow collection of ARP bolts. I traded off the old engine for more toys and parts, but left me with needing some of the small stuff like harmonic balancer bolt, cam bolt, thruster plate and bolts, etc. Just slowly working through the parts for this build.
I did purchase the 6R80 that only had 53K on it. From further research just like all Ford transmissions there are small differences between the years and the model these transmissions were installed in. They dont recommend the early models from 2009-2010, but do recommend the 2011-2013. In 2014 they changed the front pump and some of the internals for the stop/start feature that are not desirable. Also, you want to get one from an F150 due to them having extra clutches installed in them over the mustang version. This means the best one to get is from a 2011-2013 F150, which I got a 2013 F150 model. There are some small items again that will be needed like a new crossmember, shifter lever, transmission cooler adapter fittings, etc that all can be purchased from PBH (Power By the Hour)
Next was the adapter plate to mate the engine and transmission together. I was going to make my own, but found another supplier of the plate that's made of 3/8 thick steel. I just need to purchase the necessary hardware to mount the adapter plate and for the transmission. Went ahead and grabbed it, so it should be here this week as well.
Lastly, this item I was worried about due to the issues Mike ran into with his car. Since the adapter is adding a 3/8 gap between the engine and the transmission this is of course going to mess with the torque converter mounting and the snout that rides in the flexplate. I decided to give FTI a call to see if they have done this type of build before, which they then put me on hold asked around saying no but... If you are willing to test out the converter for us we can make one for you. They of course need some measurements of the adapter plate, torque converter snout diameter, and converter spacing for the feet. I decided to go with there triple disc as it gives the most flexibility of lock-up in every gear, and can handle 1000hp, which wont be anywhere near that on this build. For the price already paying for this might as well put the best in there.