Timing 12 initial 22 total?

[DuallyFlatbed]

Hey guys, my first post!

I picked up a 70 c-30 about a month ago and have been trying to get her running right since.( it broke down halfway home, flooded out)

Its a 283 out of a 65 c-10, with a 68 buick lesabre quadrajet on top. Atleast thats what my research shows. Im assuming motor is fairly stock built.

I rebuilt the carb and now shes running ok, but i figured i'd give her a tuneup before i go break down again. I'm trying to set the timing but thats where im running into problems.

I set her to 12* intial, dizzy vac unplugged.

I reved it where the timing stopped advancing and got 22*. (no tach to go by)

Shouldnt it be around 34-36? With the dizzy vac hooked back up i got around 41* before it stopped advanceing.

Its a points ignition, and i just figured out how to use a timing light 2 days ago. Any help would be appreciated guys.