63Impala5.3

I have a 5.3 lm7 with slightly ported heads, ls6 springs, headers and holley super sniper. I upgraded the camshaft to the sum-8714r1 stage 4 low lift truck cam. 226/230 112 .550 lift. (MSD 6014 ls box). it will turn on and rev but will backfire, I have the msd box set to truck for the timing. I know I need to adjust it and wanted to know if anyone had something similar with same specs that already have a tune they would be willing to share.or some advise and point me in the right direction.