engine swap question?

I have a 1970 4.2 XKE roadster that needs a new clutch. I have a chance to buy a rebuilt 3.8 engine that came out of a 64 Mark II. My presant engine is ok but seeing as though I have to pull the engine anyway I was thinking of putting this one instead. What problems, if any will I have?

Take a good look at the engines oil-sump, E-type has the big 'coffin' (don't know the name in english) part# C.16750
The MKII has the same sump but with an extra box underneath welded to it part# C.24502.
Maybe somebody else knows if this is for extra oil-capacity or something. But do mind if the larger sump will fit and doesn't come to close to the ground.