Transmission/Engine Angle?

[Chillin014]

I am considering fabricating up a new transmission crossmember for my 81 El Camino and realize that I need to take into consideration the angle of the transmission relevant to the rear end. From what I've read they are supposed to be angled equal degrees in "opposite" directions. Correct me if I'm wrong.
But if I am not, how many degrees is reasonable? Or do I just imitate whatever my rear-end figure happens to measure at? I assume I am to measure this with the vehicle on the ground?

Here are some diagrams I found.
http://www.streetrodding.com/index.cfm?f=pics.view&id=463055

 

[kevind]

I normaly have the carb flange level on a Chevy engine that way the engine/trans will normaly take care of its self. I have ran the rear end at up to 5 degrees down with the engine set this way. Anything much more than 5 degrees on the rear and pinions don't last long.

 

[Chillin014]

okay thank you! I will check what the rear end is at since that is the one aspect I have no control over anyways. Where do you suggest measuring on the rear end? on the pinion yoke?

 

[kevind]

The pinion yoke or the flange for the diff cover.

 

[Robert1320]

Actually compare the engine damper to the pinion yoke.