Setting engine/trans angle?

[jasonz28camaro]

I’m in the process of modifying my transmission crossmember on my 68 camaro for my swap. I’m using my stock front subframe and the car is currently empty except the motor/trans and rear suspension and no front sheet metal either. With the car sitting up high with the lack of weight what would i use to help get a desired angle on the motor/trans? At this time I’m only worried about the motor/trans angle, not the entire/final driveline angle. Would i use the subframe as a zero degree reference? By the way the car is sitting on all four tires.