Only just seen this thread, all i can say is WOW. What are you using to sand the engine smooth? and can basecoat/clearcoat be used on engines?
Just a quick thought - have you tried a ceramic disc on the angle grinder - they last longer and stay sharper. Much less hassle.
I can't imagine the time needed to prepare parts to that standard. I'll do a little work to stop things from rusting too much again and then keep the bonnet shut, but your photos are in another world. Big respect for that - would drive me mad.
Where do you buy your sanding rolls from like the ones in the last picture. I've been looking for a set for some stuff I want to do on my Mini head but all the kits I've found are over £60.