I would measure the drive train loss at 20%.

I believe that running 11 to 1 compression on the 276 cams would be more effiecient. Exhaust may have some effect too not knowing your size.

It would also be good if you could get an A/F ratio per 1k RPM.
also ignition timing. Since it is running slightly rich you could bump the timing 2 degrees more advanced to see what results would be. (what is the TOTAL advance now?)

If you have adjustable cam gears on your car you could play with them to achieve more initial compression.

Good luck!