Not a real productive session, but I did make some progress on the F-704 spacer blocks. I am using my belt sander to bring 2x4's down to a thickness of 1.438". They are pretty close and I only need to remove about .050". They are both close with a little bit to go.
I will be ordering replacement F-605C bar doubler, F-705H 1/4" bar stock for shim, and a F-634L seat belt anchor that isn't drilled quite right. Parts will be about $30 plus shipping.