Modern Fluids, Classic Pony

I can help you with all except the steering gear. The manual trans will need a gear oil rated GL4. with an 80w viscosity, Pennzoil definitely makes this, but not sure about availability in the UK. I would guess that Castrol and others have an equal product. The key to this is NOT to use a GL5 rated gear oil, this gear oil contains additives that can damage the syncros.

For the rear axle you need the GL5 product with a 80w90 viscosity, the additive your transmission does not like is needed to protect the ring and pinion gear from wear. You should be able to find this pretty easily, it is used in nearly all differentials. Pennzoil again has this product, again others will have a comparable product.

for the rear i like a 75w90 part synthetic, if you have a posi, dont forget a bottle of gm or ford friction modifier. although on some of the bottles of rear gear oil it says it contains this additive, usually in the fine print it says only for topping off, you will still need the friction modifier. but once again this is only if you have a posi or t lok. most any rear gear oil anymore is gl5 gl4 gl3 etc certified.