It helps to use an angle finder. You need to set it before you install the drive shaft. This article shows how I set my driveline angle to match my existing rear end angle. You'll be going the other way but the principle is the same.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.