After looking over the Red Line MTF specs I wondered how Motul Gear 300 would fit in. I did a compare using Widmans viscosity graph and came up with this:

If the numbers in the PDS are to be believed, then the Motul oil really is a
70w90 and not a
75w90. It looks like the Gear 300 is equal in viscosity to Red Line MTL somewhere around 1C and is thinner as temperature drops. At 100c the viscosity is just about equal to MT90.
These are excellent numbers if they can be believed or verified. I'm curious if there is a similar gear oil that is a bit thinner that might be a better all-around match for manual transmission use that don't need the SAE 90 gear-oil spec.