2wd blazer 6cyl, gas in oil!

[Jake's 72' blazer]

ok im a new member here any help would be appreciated. i have a 72 2wd blazer with the 250 inline 6. it has been bored .30 over and has a cam and headers. It has a 4 barrel offenhauser intake on it. along with this was a 2 barrel holley carb w adapter plate. this was all done 15 years ago by my fathers friend. i could never get it to run right with this setup. It allways backfired and sputtered like crap, even trying all possible timing settings. (because someone said it could be the timing)?? so then i went through the carb and now it is basically just dumping gas into the oil. must be something i did to the carb?? and also what carb and intake settup should i run? get a 4 barrel or get a 2 barrel? get a stock intake or leave the offy? i just want to be able to drive it. thanks in advance, i figured i came to the right place.