How far can I de-arch my monoleafs?
 

I am thinking about 4".
after that I will use Airbags to adjust to the right ride height.

I think you can buy soft, like 35 pound mono's that just locate the rearend and the weight is carried by either a coil-over or an air-bag like you are talking about doing..

Check the roundy-round parts places here...

pdq67