Seems like everyone at the airport stopped by over the last two days. So the was only slight progress was made this weekend.
After talking with an A&P I changed out the castle nuts on the engine mount to MS21045-7 metal stop nuts. Same torque and retention capability and no cotter pins to fight.
Finished riveting all the various components together and installed all the baffling components on the engine and checked for fit and finish. Then I started fitting the oil cooler. It needs a little trimming to have space from the engine mount and the oil lines.