My thoughts and past experience comparing your combo to what I put together back in the mid 80's. You have a Good combo of engine parts. I Personally do not think the Big dome or intake is hurting you at all. What I do know is you got to gear a 427 like a small block. Especially when using a PG. I also think you need more stall/flash from your converter. Something around 5700 to 6200 stall/flash. I would have a minimum of a 5:14 rear gear. I my self would have a 5:38 or a 5:57 in the rear. Then make the 4 link work for your cars 60 footer. I would be shifting that Bad Dude more closer to 7600 to 7800 r.p.m.s. I think your car is capable of mid to low 9's with a gear & converter change. Another thought, when is the last time you had your converter checked ??
The combo I put together back in the mid 80's had a old Edelbrock V Jr. The one that had the twisted/angled carb & a modified 850 on it. A Crower solid lifter cam (not a roller), 188 iron ported heads w/ 2.250 intake valves, 13.1 compression, 6.135 7/16's rods, GM 427 crank. A Good Basic 427 build. The car is a SG style ladder bar a-arm car, weight was 2500 l.b.s. race ready. This chassis by no means was up to par. The first night out with the car, it ran 10:00's @ 137 m.p.h. I couldn't run any faster because I did not have the SG licenses. Later in the year with another guy driving the car, it ran some 9:80's with no other changes. The next year we maid a head & cam change. The car picked up a bunch ever where. The e.t was down in the low 9:00's and m.p.h went up to 143. The guy that owned the car was a Bull head. The chassis & springs were set up for a Military truck. I felt with the correct changes, that car was capable of running 8:50's easy.
One last thing, the 427's do not get the respect it deserves. People refuse to believe they just got beat by a small engine.
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Ron 92Camaro