A lot of people are putting up projections pretty similar to what Clemens did the last time he was in pinstripes, which would be a mid-3's to high-4's ERA. Personally, I think Clemens has actually improved since then. I realize that the league switch probably helped him, but your ERA doesn't drop by a run and a half due to league change alone. If you translate what he's done the past couple of years (1.87 ERA, 1.01 WHIP; 2.30 ERA, 1.04 WHIP) to the AL, I think you're going to come out with better numbers then what Clemens did the last time he was in New York.
I'd guess something like this: