383 Help/Questions, Long Storage, Unknown Parts

68 383 HP with 906 heads.

Picked this up and sold my other 383 because it appeared to be in better condition.
Apparently it was in long term storage, a few years maybe, and was going to rebuild.

Here goes:
What's up with the white-ish valve color, on all of them?
Why are the rods a rust color? They look like they have surface rust, but in the pics they look different.
Are the rods supposed to have play on the crank front to back?
Purple flakes in the pick-up screen, looks the same color as the cam, what's up with that?
What say you on the plugs? Some have some black stuff on them, they're all the same plug so my guess is they were run in it.
Turns over fine, is it safe to put a starter on it and check compression on the engine stand?

Oil pan was full, oil looked good. It had some minor sludge pieces which looked white-ish and further inspection revealed those to be insect carcasses.

Looks like it was rebuilt and they used the stock rockers, and possibly springs, but I have zero info on it.
Just want to check it out the right way and understand some things before I go any further and install it.

Thank you fabo.

20200930_152449.jpg

20200930_152502.jpg

20200930_152508.jpg

20200930_153049.jpg

20200930_153735.jpg

20200930_171820.jpg

20200930_172048.jpg

20200930_172003.jpg

20200930_174259_001.jpg