Usually when a Blackface mod is done to a Fender Twin Reverb the only real differences are in the Power Transformer and output section. The preamp sections are relatively the same with the exception of master volume and push/pull master volumes. So if you are going to just use the preamp section, you can pretty much use any of them to start off with. This does not include material choices used within the different eras, just the circuits. What Blackface lovers love about the AB763, again not from the superior parts materials used over other twins, is it's output section when used as the traditional combo amp. This is where and what the Blackface mods usually entail. Not including the needed swap to the slightly higher output voltage of the Blackface era Power Transformer.
Fender Twin Reverb AB763 Output Section Highlighted.
For those of us that use the Fender Twin Reverb's preamp section, we dissect out only that portion of the circuit. This is what Brad Sarno and Dan Lurie have done with their preamps, so neither of their preamps are actually "AB763" because it is essentially the identical preamp used in the Fender Twin Reverb AA270 or AC568 or AA769 circuits.
hope that helps,
Disclaimer: I only make, modify or build things for those that seek what i may be able to provide.