74.5 rear frame loop locating dimension

[derek martin]

I'm fixing to replace the rear frame loop on my 74.5 250. The original has been tweaked and straightened, cut off and rewelded many times judging by its appearance.  I need a dimension from a point of reference on the centerline of untweaked frame to the very rear of the frame loop so I can cut new loop / old frame and position the loop correctly  making the repair as close to original as possible. Being a bit meticulous here I know. Thanks in advance for the help.