That engine should at least be 320 horse to the rear wheels and about 370 to the crank.
The torque should be over 400 foot pounds.
Something is way off and i am willing to bet that it's the carb.
I would not be so taken back if it was a 318 with stock 318 heads.
BUT...........you have a 360.
Lets put it this way.
A good running 318 with your set up could go 13.50 for sure.
Now take off 4 tenths of a second ET just for the increase to 360 cubes.
You get 13.10 ET'S......
Your 360 has a very good cam in it and everything is ready to GO.
I would say that the converter was holding you way back but with the low mph that you have ,it isn't just the converter.
Your not making your max horse power.
That engines good for another 50 horses..........:thumbup: