Fuel/air mixture screws are for idle only, and you say that's OK.
Bad performance once you're on the throttle can have several different causes.
* Float too low
* Insufficient fuel (clogged filter)
* Dizzy timing advance not working ... or leaky vacuum hose to the advance.
Insufficient fuel supply can be tested simply by going wide open throttle up a grade, which is when fuel demand is the highest. If you get lunging or cutting out, replace fuel filter and pickup sock in tank. There's no shortage of bad socks reported and discussed here.
Jeepasaurus (Wagonus Grandi quadropedus)
88 GW 360-.030 over/2150/727/229/Posi, e-pump, AC (broke), tow package, Monroe Air Shocks, TFI, CTO-Free, AIR-free, oil & tranny coolers, dried knuckle blood all over, GM 350 TBI in a box, waiting...
"You're an FSJ'r when the parts guys memorize your name, phone & credit card#."