From talking to ILLusion last night I got this info. The P90 box should be pretty similair to the V2,V3 and like all good bullpups it's only two screws and the whole box falls right out...GO BULLPUPS!!
Compatibility: BY ILLusion off of ASC
Piston: v2, 3, 6 (some pistons are v6 specific)
Version 7 is specific, although v2, 3 & 6 can be modified
Gears, v2, 3, 6. v7 is unique.
Piston head: Compatible across all versions.
Spring guide: all versions specific. Some manufacturers/models allow v2 & 6 to swap. Some allow v 6&7 to swap. Some allow v2 & 8 to swap.
Springs: All version specific (minus PSG-1)
Anti-Reversal Latch:
v2&3
v6
v7
Cylinder Head:
All versions specific
Nozzle: platform specific
Tappet Plate: All version specific
Cylinder: v2, 3, 6, 8 compatible
v7 specific
Not sure what it is you're looking for exactly, so that's just some stuff I've listed off the top of my head. If you're more specific, I can be more specific.
There is some gearbox information that I did not list due to unfamiliarity with them, such as version 1, 5 & 8.
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As far as I know, all ICS and TM parts are interchangeable, except for the anti-reversal latch. ALL TM compatible latches can fit in ICS, but the ICS latch can not fit in to a TM gearbox (or clone) without destructive mods applied to the shell.
TM compatible bushings are a little bit tight fitting in to ICS shells, but it's doable.
As far as I know, all bearing/bushings are cross compatible except for version 6. Version 6 is unique.