Thanks to Dean, I was able to procure a replacement firewall bracket. I swapped it out tonight, then went for a drive. The pedal feel totally changed, and now I could feel the break where there's more resistance and I'm getting into the secondary. I could feel a quicker acceleration, and it didn't run out of wind at about 3000 rpm, it just kept pulling. After jumping on the highway and going up an exit, I pulled over and popped the hood. The paper clip on the secondary actuator shaft had moved! For the first time ever since I have owned this 40! Why didn't I discover this sooner!?
So I took it down to Ricardo's test track, aka Surrey Ridge. I hit the bottom of Surrey Ridge at 3000 rpm (about 65 mph), and once I was on the incline I floored it. Fairly quickly the rpm krept up to just under 3500 rpm (about 76 mph), then slowly bled off on the upper portion, getting down to about 3250 rpm (about 71 mph) before the road leveled off again. Since my speedo is broken that's the best I could get for now. I did those calcs based on 30" tires, since my 31x10.50 MT/Rs are worn and I'm not sure what diameter they started life with.
Not a huge difference, but I have more available power than ever before, and it certainly pulled that hill better than it ever has! I can't wait for the I-70 hillclimb next weekend on the way to the Argentine Cleanup!
Now, I wonder how many 2Fs have been ditched for V8s because of a similar problem?