I know it's a big difference in rear gear ratios, but my brother had a 3-speed OD in a Cuda that he stuck a 2.76 gear in for a month long drive around the US and the AC would not work properly at 65mph because the compressor was running too slow. And I'm with Doc, big valves are gonna hurt performance at the kind of rpm you will be using the most, I would go stock 2.08/1.74 if possible.