350 sbc stack fire

[mud slut 350]

So heres how the story starts. I was out trail riding all was well truck was running great. progressively the truck would start to stack fire when i gave it gas and it was under a load. after progressively getting worse for about an hour it finally got to the point where if i even touched the gas she would die out but would idle fine. we pulled the distributer off and cleaned all the contacts with a rag since there was a little bit of corrosion on them and a lil damp also. we put it back on and she didnt even start. just turned over and lit the carb on fire. so obviously timing was jacked up. we advanced the timing (turned clockwise) and she fired up and ran, although had some spark knocking she got us out of the trails and home. at home pulled the vac advance off and found it was bad replaced it and set the timing to 8deg with the vac advance unhooked and plugged and the line was rock solid at 8 not jumping around at all. that was about 2 weeks ago now it still stack fires really bad when under any load even though the timing is still rock solid at 8 deg. I dont know where to go from here think it could be a tuning problem? It has a edeljunk 650 on it that hasnt been touched in about 6 months or so. any help would be awesome! also am thinking about putting a regular HEI dist on it to get rid of the esc bull. So if anyone has any comments on that also... truck is an 82 k10 350 sbc,sm465, np205, dana 60 front, 14bff rear.