I read the thread that the 1987 isn't loud enough. I'd say it probably has more to do with speakers though since for my 1987 the volume difference between a 1x10 and 4x12 cab is night and day. However assuming that you keep as much part as you need (like using the same transformer) what kind of modification can one do to a 1987 to make it louder or increase its headroom without buying a new amp? I was thinking how about changing the power tube from 2 EL34 to 4 6L6? the 6L6 has less heater draw so I think the transformer could do it...

Wow...not loud enough?? 

My 1987 is ear splitting loud through a 4x12 and a 2x12. I need an attenuator to tame this beast. I guess you could change the tubes but then it wouldn't really be a 1987 anymore?