The cost of what a new low gear for a 727 goes for will be a good start towards a 904 with a low gear + longer driveshaft. (Selling the 727 related stuff will also help.) Back in the '70's, Chrysler did a lot of trans testing and the results showed that with all else being equal, a 904 was .15 faster than a 727 due to less rotating weight. Then you have the added benefit of the available 2.74 low gears from later 904s. The results will vary based on weight, rear gears and torque curves. I believe that a lighter car with a bigger engine/longer stroke will benefit less than a heavier car with a smaller engine/shorter stroke. A low gear in my 360 dart helped a bit, but it weighs well over 3,500 lbs.

(But if it's a big block, the 904 suggestion is not applicable.)


A online calculator could show how much more gear you can get by with - at least a step or two.

Also remember that the suspension and tires will also have to handle the extra torque multiplication from more gear and power.
Were the tires hooking the same with the converter comparison?

Accelerator pump tuning can help with 60' as well, which "might" need adjusting with gear/converter changes.