Firstly what you want, then what your first name wants, then what your surname wants - Lampros

At your risk. Obviously we respect the freedom of others.

Is it possible to build the Pleiades single transistor 2N3055 power amplifier using the heatsink itself instead of a metal box or vice vrsa?

At your risk. Possibly using plexiglass on the sides of the heatsink to mount the Neutrik RCA connectors etc. Would for example 8 AA batteries in series with the safety fuse fit inside too?

On improving Le Passific 2SK170 JFET MM RIAA Pre by Walter, Hiraga?

According to the trusty Tube Preamp CookBook - Allen Wright, while disc cutting treble is not increased above about 50KHz so while playback the inverse RIIA network should stop decreasing above 50KHz. So a resistor should be added in series with the capacitor cutting high frequency on passive networks. See Chapter Circuit Modules...Passive 5. This should give more air and life to the precious vivyl records. How would this neat trick sound on a DCC90 (3A5) Pleiades battery powered RIAA electron tube preamplifier?. How would it look made from plexiglass? Would an MC to MM stepup be needed made with transformers inside Neutrik modules, cylindrical or rectangular for example? Vinyl makes better men (women) of us all.