[Roadsters] Manifold Stud Questions

[Eddie]

Hi guys,

Found something that strikes me as weird, and wanted to know what the 
deal is.

I've got 3 engine heads for a 1600 Datsun Roadster.  (Have one car, a 
parts car, and part of a 3rd parts car)

1 is a cast iron head, (my roadster had a forklift motor in it when I 
bought it.  Yup, with the forklift cam, oil pan, everything...some 
bonehead literally dropped a forklift motor in the car without making 
ANY changes at all to it.  Duh.)

2 are Aluminum heads.

The cast iron head uses 5/16 x 18 studs for the exhaust/intake manifolds

ONE of my aluminum heads uses the same size English bolts.

my OTHER aluminum head takes 8mm x 1.25 studs.

Is this normal?  Were some of these metric while others were English?

Also, I took the water pump off of my spare car, and found a 1" thick 
aluminum "spacer block/plate" between the pump and the engine.  My other 
2 motors did NOT have that, and the book doesn't show one.

What's the story on that?

My questions are more out of curiosity than anything else, but I would 
like to know what's up with this stuff...

Thanks.

Eddie