spring relocation inboard help

1972 dart swinger, A-body 8 3/4 rearend with the small bolt pattern axles, stock drum brakes. I want to run a 275/60/15 tire on the back. What do i need to do to fit this tire? Will the 3/4 " (1/2") offset shackle kit be enough or do i have to do the 3" spring relocation kit? I can NOT roll the fenderlip due to bondo in that area. Im beyond ready to get more tire under the back of this thing.
Thanks!