I can see the alignment being an issue its more resistance and more friction going forward ie more power being used to push the car especially if you have a toe in or out. I know on my dart the tie rods where off and the tires were to toed in and it wore the tires out quick thats alot of extra friction in the front if the car for the engine to push it in a straight line. I'd say a good alignment is worth at least a tenth!
I don't know enough about carb spacers to comment however I did see a dyno video on youtube were a guy had pretty big gains by adding a 1 inch spacer.
