I have a Heritage Std 80 with Shaws. Back in the day had slightly lower output than the T Tops in my 1978 The Paul. My current SGJ has the 61 reissues, and they can be hotter than the Shaws, but I've dropped them to where output is equal. The Shaws have more output than the Pat #s in my 1966...
Clapton played a Burst because that`s what there was at Selmer`s Music (a salesman sold Eric his personal used instrument against store policy). Clapton wanted a P90 Goldtop like Freddie King`s, but therre wer no Goldtops in the UK at that time.
I dropped an SG HP board into my SG-J with 5 wire 61 pickups.
Works great, I have taps, splits, and transient suppression, along with lower friction pots with a better taper.
Took maybe 10 minutes all told.