I feel like I've read every paint thread on this board...
Off the top of my head, here's my summary:
Cases, jugs, head, etc:
As Magpie recommended, Duplicolor 1615 is probably the best color match, and probably the most cost effective option. Reviews here are mixed approx. 50/50 on it's durability. Don't expect it to hold up to gas for any extended length of time, nor does it do well under pressure (areas under the bolt heads - not that you will see that - but that will be a failure point that can grow). I ended up using it on my build as it was convenient. I expect I'm going to be doing some touch-ups periodically. On my next build I'm going to seek out some professional advice if I want something more durable. Probably not a DIY job unless you're good with a 2-part paint gun or are a professional powder coater. This route requires more money and finding someone who's also passionate about doing the job (there are a lot of crappy painters and PC's out there).
Clear coat (case covers and valve cover):
Multiple posts here about problems with Duplicolor's high temp clear coat turning brown, as JeffSTL pointed out. So stay away from that. Clear coating bare aluminum is a challenge - especially old aluminum that might not be perfectly clean. Most people here just buff and periodically apply a quality polish (autosol, mothers, etc.).
If you're going for original restoration and decide to clear coat, don't get your expectations up on durability.
I think I'm going to do a test of one of those 2K paints sold on eastwood to see how they hold up to heat.
There are some clear powder coats, but not marketed as high temp - seek the help of a professional if you want to go that route. There may be more information on the sandcast forums on clear coats, as original is more important to them.
Good luck.
