710 & 714 are both megane blocks, the 714 is just the later versions of the car. The spider is 712.
The 710 block is virtually identical to the 700 with the same crank as the diesel
All the others have a different crank as the oil pump is chain driven straight off the crank itself, they're very very similar in their construction & how they work to the F4R which was basically a development of the later 712 & 714 F7R's.
The megane heads are all the same though, same small ports, 33mm inlet valves & 29mm exhaust valves. They make slightly better power & torque than the williams lump and that's with a milder cam profile. Fitting williams cams to a megane head will give you a significant improvement as well as they're more aggressive