78-79 Alt Pulley Differences A/C & Non A/C Equipped?

[6Shooter]

I'm looking for a 78-79 SC Alt Pulley and saw that someone had specified a NON A/C Alt Pulley.
What is the difference between an A/C equipped alt pulley and a Non A/C alt pulley? Pulley O.D. Diameter? Would the A/C equipped alt pulley have a smaller O.D.? Would the eng lid A/C condenser impeding or heating air flow be part of the reason for a different pulley?
I see that there are different Alt Pulley #s:
930 102 028 01
930 102 128 01
930 102 028 09
Does anyone know the differences / advantages /improvements of one over the superseded ones? Thanks for your time.

[6Shooter]

I found out that the SC A/C alt pulley has two grooves. My 73 2.4 had A/C but the A/C belt went from the crank pulley directly to the A/C compressor. (FWIW, my A/C compressor has been a door stop for over 20 years since it was both heavy and in the way for valve adj.) Does anyone have a pic showing 78-9 or 80- 83 SC A/C belt routing? Are 84-89 Carrera A/C the same as SC? TIA

[kuehl]

I am no way an expert on the 3.0 engine, however:
I believe the alternator belt runs against the outer side of the engine cooling fan, that you might call the inner pulley sheave wall, and opposite that is the what you might call the outer "alternator pulley" sheave wall. If you do not have AC this belt is driven by a single groove sheave or crank pulley that is adjacent the end of the the crank itself.
If you have AC the AC belt is driven on 2 groove sheave or crank pulley and the AC belt is positioned in the outer crank pulley groove.
If the engine has an 'air pump' the alternator pulley has an additional outer belt groove that drives the air pump.
Its simply groovy design.

If you review the Porsche PeT pages for 78-83 in the pdf version that available from the Porsche site (at this moment)
https://www.porsche.com/usa/accessoriesandservices/classic/genuineparts/originalpartscatalogue/

CRANK PULLEYS
Illustration: 102-00
you will see there are 2 versions of crank pulley's, you got pos "12" which are probably the single groove crank non AC pulleys,
and the pos "12A" which are factory AC two groove crank pulleys. You got versions of both for certain years of non aspirated (SC) and
blower or turbo versions.

ALTERNATOR PULLEYS
Illustration: 105-00
you will see pos "8" versions for certain years, and again non aspirated and turbo.

If you view illustration 108-00 you will find a separate listing for pos 35 for the special alt pulley section for air pump engines.

Benefit of one over the other, can't say. Someone older than me can probably answer that. lol