I just installed my summit 1 inch carb spacer and all I can say is WOW! On the way home from work I was punching it everywhere so that I would be able to compare it once I got home and installed it. I did notice a little loss of torque below 2000 especially when in 5th with my .63 overdrive, but whe you pass 3000 it pulls like the world is coming to an end!! well not that hard, but pretty hard. It made a VERY notice able SOTP difference on the top end, and yes it now pulls to 6500 no prob. I am feeling 11's soon if this wind would die down.

 

Congratulations. Nothing like actually trying it and seeing if it helps.

Sounds like the added plenum volume and the ability for it to get some "cross-talk" from one side of the carb to the other really helped out in your case.

My expereince is that if it liked an open spacer it will probably like a switch to a single plane intake, too. Something to keep in mind for the future.