I feel for you pal.
I have just had a look at your project thread and I noticed something about the camshaft that you should check up on. The top of the lobes are nice and polished where it has been contacting the tappets, but the dwells are coated with varnish. I mentioned it before, but you may want to check the tappet clearance to see if it is too big. I don't have the figures to hand, but the figures should be mentioned in the haynes. If this gap does not close up, then the tappets will sound. This means that either the tappets are at fault and not pumping up for some reason, or there is no oil getting into them.
By the looks of your old, new tappets, they are turning as advertised when the engine is running, so no problems there. They are just not pumping up.
If you feel the urge again, remove the cam and get a very light peice of ferous metal that is not magnetised. (Sprinkle some iron filing on it to make sure most of them don't stick!

) Then position the ferrous metal in close proximity to the valve stem and collets and see if it is attracted to them. If it is, then your valves are polarised.
I know I harp on about magnetism, but some people get away with it, and some don't. Something is preventing the tappets doing their job and you need to find out why.
Failing that, you can fit old school solid ones, but these are a pain to set up and require adjustment by adding shims underneath them. So its cam on, cam off until you get it right. But when it's all done, you will always have some degree of tappet noise. That is the nature of solid lifters.