[ADDvanced]

So I have a 77 targa that runs pretty great, although it leaks oil quite a bit, it's generally pretty reliable. Yesterday, on my commute home, I was cruising at around 80mph on the free way when it had a pretty major hiccup; the engine quit, the tach dove downwards, and the car almost felt like the brakes were on for a second; I felt flung forward. Then it resumed normal driving.

A few seconds later, it did it again. Then normal driving. Then again. Then normal driving.

When I got off the freeway, it acted normal and drove without any issues.

The hell? Any ideas?