Brilliant photos Ken. Lothar was one of the great Can-Am privateers, and raced several McLarens throughout. He managed to get his hands on a couple of the factory team cars after McLaren was done with them, including a 1969 M8B, which he raced and crashed a couple of times in 1970.
The Sam Posey McLaren was prepared by Ray Caldwell of Autodynamics. Caldwell and Posey were a partnership for several years in the Can-Am, and including the construction of the Caldwell D7, which I think was funded by Posey. He came from money, and could always afford top equipment.
Posey and Caldwell approached Chrysler Corporation about running a factory supported car in the 1970 SCCA Trans-Am series. Dan Gurney's AAR got the gig to run a pair of Plymouth Cudas for himself and Swede Savage, while Caldwell and Posey ran a Dodge Challenger for Posey. They had a pretty rough season, and never won a race, which Chrysler wasn't too impressed about. The relationship between Posey and Caldwell soured as a result, and I believe they split at the end of the year.