ok since this is already going there i will give my three cents worth.
with a underpowered car, anything with under 200whp, the manual will be faster, quicker, over that and the auto will be better in the 1/4. just something ive obsevred in my years.
autos can handle more power. if you dont believe me look at the specs on any car with a towing package. all the bigger towing numbers are with the auto not the manual. with a manual tranny you will be inconsistant and that sucks for bracket racing. what type of drag racing do you plan on doing?
autos are easier to make go quicker for less money than a manual. drop a trans brake a big stall converter in an auto and gain a sec or two.
the original question was about a standard or a 5 speed auto. im not sure wich standard tranny is in the mustang but we will assume it is a 5 speed, since a mustang GT has never been offered with 6 gears. so he asked wich was better, both being 5 speed. id say go with an auto. no better gas milage, same amount of gears.
someone on here sugested to use an 03 cobra tranny. nice idea but will it fit? and if that fits id go with a viper tranny instead, d&d sells the bellhousings to make them fit alot of other applications.
and now for a question that bothers me, why would you buy that slow 14+ sec mustang for a drag car?
i saw a company take one into the 12's they needed to completly redo the suspension, new rear end, take out tons of weight, put drag tires(not sure if radials or slicks) and then do all the boltons. your looking at close to 4k to get that car in the 12's
or nitrous, lots of it