Definitely check the differential pair transistors. They have a great effect on output offset voltage.
Bias is set by the three diodes that connect the bases of the driver transistors. The higher the voltage difference between the bases the higher the idle bias. The 1N4007 will work as replacements, but so will 1N4148s. There should be approx. 2 vdc different between the bases.
What transistors did you use as replacements for the outputs and for the drivers?