Nice score! I had a 78 D100 SL6 3 on the tree about 15 or so years ago. It was very difficult to keep up with traffic and the slow shifting a 3 on the tree requires made it even more difficult. I have a feeling you'll be swapping it out sooner than later down in socal.
Daing, I had a 87 or was it 88 last year for the slant, 1/2 t. 4 speed OD. Heck I pulled B bodies and such on my 18 ft car trailer. No issue once I got it rolling!!! Back in the little hills of Mo.