Sounds like a good cam choice.
I doubt you will get 11:1 with a 427 and 781 heads. Those pistons are most likely rated at 11:1 with 100cc or maybe 110cc heads, not 120cc 781 heads.
For a BBC on pump gas and that cam (294S), I would try to get 10:1.
Your leaving 100hp and 100ftlb on the table by not building a 496.