What stall speed to use?

[luvbowties]

I'm having a new 700R4 built, as present one has 'high-mileage leaks & looseness'. Going with a mild shift kit, one my reputable, local guy says will shift soft enough in normal driving and harder with increasing throttle. Using ~27-inch tires and a 3.73 differential--and this has been a quite satisfactory combo for 2-3 years.
Tranny man asked me what stall speed convertor--lockup type, of course--I wanted to go with. There will be no 1/4-mile runs and mostly around-town driving; maybe 1 @ 150-mile trip a year. Engine is stock 96-97(?) 5.7 vortec with 4bbl intake and carb and headers. And I DO use the lockup, planning to do the same w/new tranny as present one:locks up when it shifts into overdrive, yet I have a lockout switch run under dash to completely bypass the lock-up when I desire.
Knowing practically zilch(zero)about stall speed convertors, and never driven one for any length of time, I need to ask which one to go with. He says he'd rather me specify this parameter, altho' he's calling all the other shots AFTER learning how I drive and what I want to do with my truck.
Thanks,
Sam