Gear oil and engine oil change

Gonna do a full service of car and all fluids on the 98 gt555. Just want to make sure I got right stuff.
I got the castrol universal 75w90 for gear box. 5liters for 59€ which is quite good I thought. And that is 3.5 for box and 1 for diff. Is that right.
And the magnetec 10w40 5 liters for engine.

I thought it was 10/15 50???

10w 40 ok in that

Engine takes 4.5