From memory the focusing isnt that fast on the 50 1.8 but then focusing indoors tends to be a bit slower anyway so you'd be best pre-focusing.
the 50mm on your 1.5crop sensor is indeed 75mm, I found it a bit inflexible for taking everyday shots (you know, snap shot and the like) because of the narrow field of view. but for taking photos of cars it would be alright..
its a funny sort of length as its not wide enough for some stuff and not long enough for others.
