I am inclined to side with Tim in that the optimum RPM is closer to 3,000 than 2,000 (2,600 probably is on the money). You won't ever hear the engine roar at around 2000 RPM, but you will not get the gas mileage you think that you should. The problem is the carburetor. As you approach the slightest incline and step on the gas to keep your speed, the power valve will puke fuel into the venturi in a clumsy and less than precise manner. This is what kills gas mileage for these engines with these carburetors.
Modern vehicles get away with ridiculously low RPM by controlling spark timing and fuel delivery with a computer. That is how they get such good fuel mileage.
I run a T-5 with .72 overdrive and a 4.64 rear end gear with 28" tires. I can pull stumps in first gear and drag them down the road at 60 MPH. The 235 isn't screaming, but the RPM is in the somewhere between 2,800 and 2,900 at 60 MPH.
I have some 215 85 R16 tires to put on it very soon (30.5 inches). This will make first gear a little more useful starting from a stop (a little on the granny side with the 28 inch tires), and reduce my RPM at 60 MPH (hoping for 2,600 to 2,700). There is a handy table to get the exact figures that I am shooting for. I lost my bookmark for it, so I am going off memory. The seat of my pants are indicating that I should be pretty close.
Carl
