Homelite T-16 H Problems

I have a 1972 Homelite T-16 H with a 16hp Briggs. It was bought by my father new. We sold these and it has been in the family since it was new. It
backfires while running. It has been worked on by several differant techs and still can't stop the backfire. Any ideas as to where to start to fix it? I used to wrench for my dad back in the day. But that was 30+ years ago. I am also looking for fresh decals for it so I can restore it after getting it running properly. New to this forum and would appreciate any help.