Your AAR looks great! Not to beat a dead horse, but as far as master cylinders go, the one on your car looks to perhaps be the correct one for '71-'74 disk brake cars, 3461187. I don't know of any ever being used in 1970. I will also be another to go on record as saying all non-hemi 1970 disk brake cars should use the 2229171 master cylinder.
My R/T SE Challenger was built right in and along several AARs based on VIN and build date info I have seen (mine is 289xxx, built late March 1970) and it has the 171 master cylinder.
For those who aren't familiar, the 187 cylinder has the 'bump' on the front, while the 171 cylinder is "thermometer" shaped on the front.
We are restoring my brother's R/T Challenger right now, and his car originally had drum brakes. He is upgrading to disks, but after seeing what 171 cylinders go for these days, we did the next best thing and just put on a 187 cylinder, since not an original disk car anyway. Yes a trained eye can definitely see the difference but once correctly painted black as yours is, it is something many wouldn't even notice IMO.
Just another detail to drive a person crazy! It always amazes me how many parts on these cars are 1970- only.