more to consider: SM57 mic's of 1981, are not the same as SM57 today. Today's mic's are nowhere the quality of the original... Altec speaker is more of a hi-fi speaker for midrange, not necessarily a guitar speaker. The mid's & highs are a lot smoother than any Celestion. An A cab, vs a B cab will have different sounds, based on internal volume & the slight out of phase of the A cab (internally), top section. While the sounds are more than 90% identical, those differences w/ the remaining couple % add together to make a unique tone. Because the stone room is an echo chamber w/ varying wall angles (I envision round stones cemented together throughout), close mic'ing will still capture the liveliness of the room, but, nothing like a room mic. The distant mic's probably are capturing a mix of the rear of the cab, along w/ the billowing sounds of the stairwell, & then the upper room, capturing the distance. Back then, w/ tape & mixing consoles, you could not fine tune phase. It was +/- & no other adjustment. You couldn't slide tracks to lock them closer. You would simply mix things together, until you got the desired blend.