How to prepare for engine dyno?

Its a local guy that I was referred to. I will have a conversation with him prior .
I am looking for things that might not be obvious from guys that have dynoed motors before. I hope to try 2 manifolds back to back .... A Victor vs M1 Dual plane W2s.

I am really hoping it doesnt throw a rod or leak like a seive...lol
Please Please Please, post the results of the intake swap. I’m putting together a similar combo with the W2 dual plane and contemplating if I should step up to a large plenum single like the Victor.