First of all, a 6-71 on a 383 running 10% overdriven is 15.5 pounds of boost, an 8-71 at 1:1 is 14.4 #'s.
Your motor is a 377 so you'd be somewhere in between.
Secondly, a 383 8-71 motor with two BG 750's isn't too much for the street, mine is very well mannered. 850's? depends on the build. 650's? Posing comes to mind.
I don't really understand what your concerned about with this temp thing, but I would shy away from teflon for a street blower, just from a maintenance stand point.