Making headway (sorry, I couldn't resist that one).

The thing here is basically to swap every single part from the "modified" head onto the standard one, so that's valves, springs, cups, collets, rockers, spindles, a million washers, bolts, studs, nuts and a few more washers.
But before we get to that, I still had to remove the pistons, which requires the proper tool to remove the wrist pin (or gudgeon pin); this is important and you should always resist the temptation to just hammer it out, because it's just not right. Incidentally, you can also use the same tool to assist in refitting the new wrist pin. Of course piston circlips should always be replaced, but you know that.

Getting the wrist pin out, the right way.

Now that that's done, I'll leave the engine covered up, nice and snug, while I finish preparing the new head and go about measuring piston/cylinder clearance, but that's for some other time.
Now then, the first thing I did was to remove the rocker spindles, another easy job provided you have a slide hammer:

These should come out without too much grief, but if you feel that they're very tight, do not reach for that blowtorch as you'll likely only warp the relatively thin alloy. Instead, as the factory workshop specifies, submerge the whole thing in near-boiling water, have a cup of tea, and by the time you're done the spindles should be ready to come out. A kitchen sink is the ideal place to do this.

And here they are:

Now for the valves. For this, you'll need one of these:

They are inexpensive and worth getting even if you'll only use them once. Thing is, you'll probably need them on another engine, or maybe lend them to a friend... Don't be afraid of specialised tools, you can handle them!
Sometimes the collets can get a bit stuck, if that's the case try tapping (gently!) on the very tip of the stem to loosen them up. It's a good idea to use molybdenum paste (or grease) when assembling the springs and collets.

I have a little prep-work to do on the new head, I want to check a few clearances before I reassemble everything. Not to mention I'll need a few gaskets and all the parts you see above will need a good clean before they go back to work.