I see you thinking of running xo cranks one good reason to run them is that you can buy a spider less chainring from home brewed components and make a light ss or ten by crankset. Just make sure you helicopter tape the arms as the carbon marks up easily.

homebrewed take about 2 months to deliver and lie about shipping

in my experiance

And as I said previously the XO cranks are still pretty weighty, and I’d say the 120mm BCD is a negative!

Any ideas for SPD compatible lightweight pedals? (I need SPD compatible so all my shoes work on all my bikes).

So far my list is:
BBB MTB SPDs – 299g (£25 or so on ebay)
XTR M980 – 315g (£85 plus)
XTR M97x – 330g 2nd hand only available
M959 – 350g what I alread have

Are there any others out there who sell good light SPD pedals?

Ritchey pedals are meant to be SPD compatible.

The WCS V4 Ti comes in at around 250gr, never tried them though.

Xpedo do the Mountain Force ti/ti, excellent pedals, crap longevity, same as the Ritcheys IME. The former have a bush which is harder than the axle, so the axle wears out, the latter have tiny bearings which seize.

Just go Shimano, maybe stick some ti axles in some M980s, won’t take a huge chunk off though.