I will agree with what they're telling you. My '65 truck that I bought a few years ago had a cam that had a mild lope to it. Sounded cool but it was a turd for power. The truck has 4.57 gears, and the tires are around 32" in diameter and the truck could barely pull hills in 3rd, let alone overdrive. In April I changed the cam to a cam with idle to 4,600 rpm range, and had some Mexico heads refreshed and I easily gained 20-30 hp and gained a lot more torque. The truck can now pull hills in overdrive whereas before I had to drop it into 3rd gear (1:1) and rev it up to 3,000 rpm to go 50 mph. In overdrive the final drive is 3.19, because the overdrive is a 30% drop in rpms. We can't tell you how to spend your money, but if you want sound and no performance in YOUR truck go for it. As stated, it's a lot of work to change a cam, and to change it just for sound and no performance gain is money and time not well spent.