The JHS Morning Glory is a modified Blues Breaker overdrive, but with an added JFET output buffer to increase the volume. The original Marshall circuits barely made it above unity with the volume maxed (see the video below), so the output buffer is a good improvement over the original. There’s also a high cut switch to help tame single coils a bit. I wasn’t quite able to get the on-board pots to be in the exact layout as the JHS units (the Tone control and High Cut switch are reversed), but it’s close enough. You should be able to board mount the SPST high cut switch as well.
