carb problems?

ok i dont know if this is in the right forum or not but i gotta quick question.
I have traded for a 89lx with a 351w and a c4, the car has a torker intake and full length 1 5/8 headers. It has a 430 rear gear and stock converter. I swapped a silverado with a bbc for this car because it was suppose to be consistant and it aint. Heres my problem it has a holley 700cfm dp on it, the car lauches great but at around 4800 starts to pop and cut out. i first thought it was rich so i re jetted it still no good. Could my car be lean causing this. I doesent do it with a 750 vacum secondarie. Sorry so long just cant figure this ford out im a chevy fan.

the previous owner to the power valve and put 78 jets up front and 69 jets in the back. could it be going lean? The car only does this with my carb, i can put on a 750 vac secondarie and problem goes away but i loose 4 mph

i put 74 up front and 78 in the back and so far seems to have fixed it. The fuel is stock mechanical or so i figure it is. I put the carb back together this morning and seems to have fixed it, we are suppose to carry it to the track along with my ranger in the morning wil let yall know