mounts and drivetrain angle

[GM Muscle]

ok ive researched a little and just want to verify some things. help me out guys.
LSX swap into my 69 camaro, i have solid engine mounts and solid body bushings.

Should i also run a solid trans mount?
i was leaning towards yes but this seems to be a mixed reveiw

since the trans mount isnt in yet i can still set the engine angle. from what ive read, anything between -3 and -5 should be ok.
Is this correct?
Also, to measure this angle, im assuming ill set the car to where the frame rails are at zero then point the trans down from there right?

Thanks in advance guys