I’m doing my first full build and am looking at second hand forks.

I’ve got a scandal 29er with smoothie mixer on it’s way.

stem (standard?) 40
stack top 9
head tube 105
stack bottom 15
total 169

My question is how much steerer am I going to need to have, will I get away with 170?

Quite possibly as the top of the stem/spacer must sit above the top of the stem.
So long as the top of the steerer is a little above the highest fixing bolt on the stem, it’ll be fine.

Just remember that if you come to sell the forks at some point (assuming a bouncy version) they will be worth considerably less than one with say a 190 steerer. Dont pay top dollar – or keep em for life.

Thanks for the info. It’s amazing how much second hand forks go for on ebay – for a little bit more you can get brand new ones!