I love the idea of a hybrid 3L, but I am not an engine builder. Removing the heads requires fresh gaskets, fresh studs, and a specific proceedure for re-assembly. Since I'm not experienced, I prefer to leave the 3L heads on and just swap over the cams & timing gear. If you don't have engine re-man experience & want to minimize down time, I'd suggest getting somebody experienced to swap the heads or go with a port matched 3L and SVT cams & intake as I will do.
If you're using a Taurus/Sable motor, you'll be changing the timing cover anyway, so may as well swap over the timing equipment & cams from the SVT.