The biggest difference in lineage between the Distortion +'s are the different types of the cheap LM741 opamps used. The clipping diodes do play a part in the amount of clip but the opamps themselves are clipping and that is why the originals will sound notably different then a modern version. Also, the original script logo used metal film resistors in specific locations to keep tolerances tight. They just were not not the modern blue color. http://www.pedalarea.com/mxr_distortion.htm
making a generalized statement about the original script logo dist + tells me you have not opened up many or dated the ones youve opened. there are definitely a lot more differences than just the opamp, though it is an important part of the sound. That link you posted is definitely not an original 73-74 dist +. that's probably a 1976 dist +. It is QUITE different from a first issue dist + which did NOT have metal film and carbon film resistors in it. they used carbon comps throughout. in fact that link you posted shows a pedal that will sound much different than an original dist +. and much more like a block logo distortion plus. it has different diodes, capacitors, and a different opamphttp://www.freestompboxes.org/viewtopic.php?f=1&t=10295
i've opened up enough vintage dist + units (and DOD 250's), built enough, and have experimented enough consider myself a master of the dist +. Maybe I should make a dist + website to prevent the spreading of misinformation.
i actually dont think there is that big of a tone difference if noticeable at all between carbon film and carbon composition. the main difference is between metal film and carbon based in the signal path.
But i have measured a particularly good sounding original 74 dist + with carbon comps that showed a few resistor values off labeled value enough to make a difference in tone, this is something that i approximate when building mine. like i said, my buddy sold his coveted mxr dist + (and he's like a late 70's style rocker that runs his into a marshall jcm- killer combo there) I will say that the unit I have kept and played has all carbon comps. though i have used metal films for the 1M resistors and have not been able to hear a difference at times.
i have had people like tl071's in their dist +. my personal favorite has been a metal can 741 (i have not seen a dist + with a metal can) but any other pedal that was once built with its metal can equivalent is highly coveted. I have these old metal cans in my keeley 4 knob compressor clone (reason the old ross comps are so coveted) and my landgraff mo'd clone (rat clone- rats with metal cans are the most highly sought after as well).
and i never said alembic's prices were dishonest for the record. no such thing as a dishonest price. just chumps that pay ludicrous prices for super simple circuits!