292i6 carburetor problems

[292farmer]

ive got a 1972 c20 with the 292i6 and ever since ive got it about a month ago, it stumbles right after idle when press throttle and stumbles at higher rpms, me and my dad figured out it was the carb, we pulled it apart and the some idiot before had used some silicone? or some sticky gasket sealent that had actually spread into the jet and passages of the carb. we cleaned it out and it ran better but still ran lean, it runs perfect if we keep the chioke 3/4 on. we found the carb is off a a 1977 or later 292 and my dad remembers that those carbs ran leaner then those used on the early 70's so imwondering if any one know what size main jet were on the 77 and later monojet rochester mv and what size the 1972 main jets were? i cant afford a new carb so i want to increase the main jet to get it running smoother with out the choke on. it idles perfectly its just once it gets throttle it stumbles and runs lean, and yes i have replaced the fuel filter, and the pressure is 4psi after the fuel pump which im told is normal for i6. thank you for your help.