302, help me figure this out please

So I have a 1986 ford Ltd crown victoria that has some stuff done to it, but what’s important is that it has a 5.0 302, and I have converted it to a carbureted setup. I have a speed master single plane intake, a Holley double pumper with a proform 750 main body, I put in a msd pro billet mechanical advance distributor with a msd 6al-2 to run it and a blaster ss coil. The engine is completely stock besides the intake, carb, distributor, and some bbk foxbody headers. The problem I am having is that it is backfiring out the carb quite a bit, and it is struggling to run. I’m pretty sure I dropped in the distributor correctly but I could be wrong. It’ll start only when you pump it a few times and run if you keep pumping the throttle, even then it sounds like it might have a misfire and it still backfires. I think it is either something with the distributor or it’s running lean. Please drop some wisdom on me and help me fix this. Thanks, Henry.