Here's your cam specs:
This hydraulic roller tappet is used on the 5.7-liter H.O. engine assembly for ZZZ through ZZ2 engines. Use with spring P/N 10134358. The duration at lash point in degrees (intake/exhaust) is 336/336; duration at .050" tappet lift (intake/exhaust) is 235/235; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 480/480. Valve lash is zero/zero and lobe centerline is 114 degrees.
That's a fairly radical cam, but what the heck. You already have it. With 1.6 rockers, your lift will increase to 512. You need to make sure the springs are up to it (no coil bind), and that you have adequate valve-to-piston clearance.

With the 2.75 gears, the 700/R4 and the 31" tire, you'd be turning 1461 RPM at 70. With the 3.70 gears, it goes up to 1965 RPM. Your gas mileage would drop approximately 25% with the lower gears. My '93 Corvette with 2.70's got about 25 MPG overall (town and highway). With the 3.55's I put in, gets about 20.