Ahh, now here is a topic after my own heart seeing as I am working on a pre-heresy Thousand Sons army. First off, background on armour and vehicles - I'm one of the Background moderators on
The Great Crusade, a dedicated pre-heresy forum, so this is a bit of a pet topic of mine.
Vehicles
Predator Anhilators, Razorbacks, and Land Speeder Typhoons are all post-heresy designs, as are Land Raider variants like the Crusader. Vindicators were developed
during the heresy by the Ultramarines. I haven't found any definitive information on Hunters anywhere, so I would allow them. Vehicles that were available to the Legions during this period but not in the 41st millenium are Jetbikes and Marine Superheavy tanks (the 'Fellblade', which is a Marine Baneblade, and the 'Mammoth' or 'Stormsword' which appears to be a Marine version of the Shadowsword). There is a complete rundown of which vehicles were and weren't available to Imperial Forces during this period
here. Armour Types
- Mk. I was used during the conquest of Terra and the neighbouring planets, but then replaced.
- Mk II was introduced following the alliance with Mars, and was in use throughout the Great Crusade.
- Mk III was developed during the Great Crusade for use in close quarter fighting and for assault units, and was also popular with command squads and ceremonial units due to its brutal appearence.
- Mk IV was developed towards the end of the Crusade, and when the Heresy broke out the re-equipping of the Legions with Mk IV was only partly complete.
- Mk V was developed almost immediately the Heresy broke out, as Mk IV proved difficult to repair and recreate for many legions due to lack of spares.
- Mk VI was developed soon after Mk V, and there is background that suggests some Legions had it available early on in the Heresy period.
- Mk VII was developed just before the Loyalists were forced to abandon Mars, and was available to the Loyalist Legions involved in the Siege of Terra but not to the Traitors as the production facilities were moved to Terra before Mars fell.
- Mk VIII is post-heresy.
Terminator Armour was, like in the 41st Millenium, rare due to the fact it had only started being issued to the Legions towards the end of the Great Crusade. In addition, it differed from current Teminator armour, most notably the Shoulder Pads, which looked a bit like Roman Legionary armour as opposed to the rounded pads used today:

Jetpacks were different as well... the most common type appears to have been a pack that looked like twin turbofans rather than the current look:

I did actually start thinking about a Pre-Heresy list myself actually. I'll see if I can dig out what I came up with later...