Things to consider when picking a converter.?.?.?.?

What things are generally considered when picking a converter? Things that I can provide to a builder to help select the right one.
From what I gather things to provide are: dyno sheet, gears, cam, weight..... is this correct? Anything else?
I'd recommend that you call and discuss your options. There's so many different directions you can go and it really helps when the builder tells you why one option is better for [B]your setup[B] that another one.

