You don't even need a protractor...use your smart phone and this HANDY ap...
TREMEC Toolbox App
Man, I've tried using that app 100 times, but unfortunately wasn't able to make it work. I've got an android phone with buttons on the side, problem #1, but the bigger problem is the pitch sensor in the phone. You could move the phone slightly and get any angle you wanted. My drivetrain is so jacked up it's comical, yet I could get all greens on the app.
CDN67, I feel you man, been through the same rodeo.
First thing is free. Jack the rear of your car up, put it in drive, then get down and watch your driveshaft. Make sure it's straight, true, and there is NO visible wiggle.
Second is the life sucking chore of measuring your driveline angles and going crazy trying to find 2 or 3 pieces of well meant advice on the net that matches up AND makes sense.
Here's what I did, it worked for me, I have almost 10k miles on my swap and 0 vibration up to 120mph with poly engine, trans, and solid rear bushings.
Purchase this angle finder: https://www.homedepot.com/p/Johnson-...B&gclsrc=aw.ds
What I found to work for our wild angles was measuring engine angle, driveshaft angle, and rear end angle, doing some math, and finding the working angle of everything involved. You're getting ready to hear about u-joint bind, angle velocities, etc etc. Plug your ears.
Use this as your guide: https://www.drivelinesnw.com/part-tr...ngle-problems/
Get your working angles as close to one another / cancelling out as possible, and go for a drive. I used Speedway Motors adjustable uppers on my rear (there are better versions out there) to get my driveline angles set and had to put spacers on the trans mount / trans crossmember.