It's interesting to separate the crap from the handful of shots they ACTUALLY might have done in '77. I'll never believe Lucas spent too much time pining away for huge dinosaurs and stuff that nobody could do, he's not that dumb. I would hope he'd be be thinking about real, feasible do-overs that he'd get if Fox moved the release to July and gave him some extra money:

Some of that landspeeder stuff could have been painted out the old, painstakingly slow method, like Superman's wires. There's about 8 shots in the death star battle that actually look like a model shot, but merely with a better pass at the camera. And I bet he would have done some kind of re-take of the Alderaan explosion. So, maybe 12 shots?