i'm stumped.... truck is bogging down like a cheap gas FORD on a tank of DIESEL!!!!!

[jewels.]

ok, i'm stumped!

both Blue_71 and I are stumped....
i dug out my truck for the summer months, and started her up....
did an oil change, and tightened the bolts on the exhaust/donut gasket.....
drove her a few times with no problems....

and then.... problem....
in any gear (its a 3-on-the-tree), the truck will bog down if you give it constant gas....
at idle, it appears to run ok - just fine....
i can take off out of the yard in first or reverse - no problem....
if you get it on the road, and if you go past a particular RPM, it just acts as if it were choked with not enough gas.... bogs down seriously so badly that its undrivable....
you can hear it sucking serious air thru the carb.... it wont kill itself, but it wont go anywhere either.... if i got on a hill, i would probably have to give in...

thought maybe it was out of gas.... just barely made it to the gas station, filled her up, but the problem still exists....

on the way back, discovered that if you pump on the gas pedal quickly, it gets the power it originally was lacking, and the problem disappears for the small second or two when you pump the pedal... but then the problem continues to exist for a constant gas pedal pressure.... so if you pump the pedal, its jerky from the pumping of the gas, but it acts like it runs fine....

so, here is what i've replaced (these are now brand new parts on the truck)....
0. added full tank of gas to truck (93 octane, for good measure)
1. put on new fuel pump
2. put in new fuel filter
3. fully rebuilt 2bbl carb
4. replaced the HEI module with a new one

my truck has a 350 small block, stock cam, stock crank, stock bore, stock pistons, 2bbl carb, HEI ignition, ramshorns manifolds, dual exhaust, no air, no PS, no PB, 3-speed stock tranny, new clutch, stock rearend (3.73), a recently (last fall) replaced drive shaft, tailshaft yoke....

has new oil, new tranny fluid (as of last fall), new antifreeze, and even new washer fluid in a non-functioning washer system.....

any ideas? whats wrong?
here are some we are contemplating, but still not sure whats up....
A. a filter/sock inside the fuel tank - perhaps part of the sending unit?
B. replacing the bottom plate of the carb, which contains the mixture screws?
C. the tail-shaft transmission yoke sticking? (it was not a perfect install... lets leave it at that)....
D. an engine problem?!?!?

the key thing here is the gas..... if you pump the gas, it gets better... but if you increase the gas slowly and constantly, it wont go....

HELP!!!!!!
any reponses are greatly appreciated!
thanks in advance!
ciao!
jewels.