transgo or transpack??...

If I am not mistaken, B&M has two kits. Their light and cheaper kit does more just to increase line pressures than anything else, so shifts are just harder. The Transgo kit has springs and is much more involved, but their claim is that they coordinate shift timing better, and are better for your trans in the long haul. I have a Transgo kit in my FMX and it works really well.
 
I have a TransGo kit in my 89 Mustang AOD and a B&M Transpack in my '65 Fairlane C4.

The Transpack shifts MUCH harder, to the point of it almost being probably too harsh (not necessarily for the transmission, but as a daily driver).

The TransGo kit corrects a number of the inherent problems with shift characteristics of your transmission, and will extend rpm between shifts, etc. just like the B&M kit, but it is not nearly as hard. Firm, but not neck jarring hard.
 
if you're getting it for racing, you 'should' have a higher stall converter, which in turn will absorb the impact of a hard shift. The quickness of the shift is what you notice moreso than the harshness. Any shift kit with a stock torque converter is gonna give you neck spasms. My PA C4 shifts like an indy car but I don't feel the impact due to the converter I use.
 
if you're getting it for racing, you 'should' have a higher stall converter, which in turn will absorb the impact of a hard shift. The quickness of the shift is what you notice moreso than the harshness. Any shift kit with a stock torque converter is gonna give you neck spasms. My PA C4 shifts like an indy car but I don't feel the impact due to the converter I use.

How does the converter absorb the hard shifts? I have never heard that before and would like to know more if you could?
 
When you are below the stall speed the shifts are softened because the tc slips more. Mine shifts like a Cadillac pulling away from lights. When it shifts higher in the revs the tc is slipping much less and the kinetic energy stored in the rotating assembly is transfered to the rearend.