I had 3.55's in my old 340 swinger. They worked fine. I could drive about 70 no problem and got 17mpg even w/ a 750 DP.
Your 440 should run well into the 13's w/ 3.55's. That cam you have would probably like less than 4.10's So you might see an improvement. I'm guessing it quits at about 5200 and you are probably over 6 at the stripe.