Personally I prefer lockup, feels like I'm turning unnecessary rpm otherwise. There are some how-tos on the net for a DIY lockup without a computer, I believe there is a temperature, vacuum and 4th gear pressure switch required, along with a relay to disengage lockup when the brakes are applied. I believe a Corvette servo and new boost valve are two of the easiest upgrades, past that and a shift kit you would be tearing it down for clutches, etc. I've also read the sun shell is fragile and if it's a rebuild, a 'beast' shell would be the best to use. If memory serves, you can modify shift points by changing the governer (round cover near the rear) or slowly grind material off the weights until you reach your desired rpm.