GBowman The problem is the camshaft Way to big for cruising at low rpms. I have a 482 with a 587-607 and 3.31 gears and have to be careful not to lug the motor on cool off laps.
3 choices, use more rpms and go with a lower gear in the trans.
Replace the camshaft with something in the .550"to .580" with a 112 LSA. I am sure that your motor makes 500/500+ in torque and HP but not in the low rpm range. Unless you are going to abuse this car hard, a hydro roller will do the same as a solid for street driving and extend the life of the motor. If you goto a camshaft catalog they give you all the specs for the camshaft and tell you where they make the most power and range to run in. Being your block is a 351 and your cubes are 427, you can run a little larger camshaft than one for a 351 cubic motor.
Replace the rockers with a 1.50 ratio. This will kill some of the total lift and let the motor run a little lower in the power bands. It will kill about 15-25 HP and about 10-30 ft of torque easy.
Keith Craft sell alot of custom solid and hydro roller camshafts. Give him a call with all your specs and tell him what you are looking to do. He should be able to match up a nice in the middle of the road camshaft for you.
You didn't say anything about how nasty the car sounds at idle, Some guys live by this others like to sneak up on others. Only side not is, if you are going to run a solid roller camshaft in the motor, no long term idling even with
oil pressure rollers, pins or bearings. The first sign of valve tap after everything has been setup right, start looking for damage to roller lifter or camshaft lobe going flat. Hydro rollers go 200 K miles. Solids depending on rpm and size of camshaft,rpms, valve springs, will go 3-10K mile before needing checks with good
oil and additives. If you limit your rpms to 6,000 a good hydro roller will last for years. Have 8 years on my setup, Broken rocker shafts but no problem with camshaft or lifters. Crane setup. Have learned Bigger is not always better either, just cost more in the long run.
Rick L.