I've done several Diesel to Petrol conversions (hell I even did it twice both ways to one of mine) but I always took the easy route and dropped the 2,25P into the hole left by the 2.25D

so I'm well impressed by your commitment to do the block conversion. I feel a Kennisbank / Home Workshop article in the making
So yes it's a new head, rocker shaft, pistons, etc etc, in fact apart from the block and the crank most of it goes. You can leave the oil pump and timing gear and you can excite your brains out on getting a switched feed in position II of the ignition for the coil on an original diesel ignition switch

Oh and your throttle linkage will have to be changed and the fuel delivery system will have to be modified. You can retain the flywheel and starter and the diesel bell housing but you'll have to modify the exhaust manifold of the petrol one

(don't ask) so that the starter clears it.
The up-side is that if you have a brake servo it will now work and your face will be pressed against the windscreen the first time you tap the brakes
If you have any specific questions then please ask. I think I even have pictures in the archive
My personal opinion is by all means do it, but get a complete 2,25P unit it's a lot easier.
Rob