MGB Gearbox Oil

[Keep it stiff]

I was about to put fresh oil in my re-build box, I looked in the Haynes to check capacity and was surprised to see the recommendation of 20/50, I was expecting EP80/90.

I just Googled and I see this is a common question, from what I can see the consensus seems to be 20/50 in a box with OD but better to use EP in non-OD box. My box in non-OD, 4 synchro, early 60's and will be used for circuit racing. I would prefer to use EP, would you agree?