Rebuild 904 or swap for 727?

Use performance oriented bands & clutches (Not OEM) in the 904 with a good shift kit or valve body. 3.8 or 4.2 kickdown lever and a deep pan & cooler wouldn't hurt. Other stuff has been covered - 904 is a little quicker than a 727, all else being equal. If your transmisssssion guy really know 904's, you'll have the option of swapping in a 2.74 low gear set, but you may not really need it. Also, a good QUALITY 7260 u-joint, like Spicer, will serve you well. I ran their solid versions (factory lubed & sealed,no grease fittings) on my race car for years with no issues. I haven't heard of anyone saying that they aren't recommended for the street. I wouldn't recommend a valve body without low gear braking on the street