im not quite at this stage yet but will be soon, how are u sposed to line the end of the gear box and the diff up so it is in line properly?im sure its something simple but just want to be sure

cheers steve

It doesnt matter. The prop has 2 uni joints, so will take up any misalignment

My engine will point 3 degr down.
So my diff (IRS) will also point 3 degr down.

This prevents any unwanted whobling ;-)

You dont want it dead inline.

It has to be out of line so the uj's get lubricated and work properly.

In theory you want the flange faces parallel to each other 'cos a diff doesn't have a CV joint.
But in practice I'm told it doesn't make a huge difference as long as they're not too far out. Certainly my MK BEC doesn't have parallel flanges.