We are to use all the Bible for doctrine not part of it. It is incorrect to ask for just part of the Bible for doctrine.
Is it applicable for us to build an ark?
Is it applicable for us to sacrifice a red heifer?
Is it applicable for us to build an alter and offer the blood of bulls?
????
Just asking that is.
Yes, it certainly is applicable. We are to learn about faith through the building of the ark, and taking it deeper there are many spiritual truths involved, even that through faith in Christ we have eternal life, He is our spiritual ark. We need this scripture to learn. Sorry, I have never been able to understand the red heifer at all, wish I did. And certainly, we need to know all that the blood of bulls did, for Christ is now the blood. The blood of bulls, when applied right, worked for atonement and we are told it wasn't complete like Christ's blood, but we are to learn.
We even need to know that when the blood of bulls was used to satisfy God as the blood was used to satisfy idols so God would give good crops, God said I hate your sacrifice. We need all the bible, not part of it, to fully understand.