Positioning engine crossmember help.

[rsb5772]

I just ordered my bolt-in engine and trans crossmembers from Brothers, for my '57, and need help on how to position the engine crossmember. What do you measure from to center it between the frame rails, and how do you determine the angle of the motor mounts? Do you make them level with the frame rails, or should they be angled downward? Do I need to have the block and trans bolted together and in place with the trans sitting on the crossmember to set the position of the motor and crossmember? Thanks for any help.

I ordered the crossmembers, and power disc brake conversion, and new wire harness. I have a TH400 trans from an 80's model one ton, and a mock up block. I have a few more parts to order, that are required for state inspection, and will be buying a motor once I have everything else on or ready to go on. I hope to have it on the road soon, and will start the body work afterwards.