305 Vortec in 1989 K5 Blazer Please Help!!

Ok, I am new to this forum and not too experienced with this stuff, call me a newbie I guess. I am willing to learn however and appreciate any help. I have a 1989 Blazer full sized it had the 350 tbi motor in it, i blew it up 4 wheeling and replaced with a 305 vortec from 1998 chevy work truck. The truck had 60,000 miles on it, engine was taken down to short block, bearings, ect checked, new freeze plugs, HV oil pump, stock cam with 1.6 ratio rockers which makes it about 191/196 duration and 442/457 lift at .050. Part number on cam is 10241264. Has Air Gap vortec 4 barrel intake, summit billet distributor w/ 55k coil, 8.5 spiro-wound wires and auto lite plugs 2 heat ranges higher than the stock 98 had in it. Also has 700r4 tranny with a 2300 stall corvette style converter non-lockup. Ok, here is the problem..... I had a 700 Holley Double Pumper on it with mechanical secondaries, no choke, ect. With this carb it was really sluggish off line (had deep bog gurggle sound) (too much fuel?) but ran awesome from 3000 to 5500 rpm. It was getting fuel in oil, making it thin so i swapped it out for a 450 cfm holley two barrel i had on shelf, ran ok with this carb but carb was old and worn out, no top end hardly.. I now bought a holley 600 vacuum secondaries carb and having problems with it. If taking off slowly it will do fine but push throttle down too much it will almost die it seems (drops to 1000 rpm), it will then crackle and pop and slowly rev up (keep in mind this is driving down road not in park) in park it has slight hesitation but revs kinda ok. Has about 60-70 lbs oil pressure at idle. Has about 19" vacuum at 900 rpm in park, timing is set about 10-12 degrees advanced at park with vac adv unplugged. Stock tbi electric fuel pump with regulator (have tried all pressures from 4.5-7) Any ideas whats up with this truck guys????


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might add, has 6.5 power valve and all stock jetting, ect for carb "supposed" to be bolt on and go