jbaj007 did that many years ago. 124 and 126 economy gauges have about 7 psi between posts. I set the indicator to lift off one post at 5 psi and peg at 12 psi. That means lifting the indicator over the low end post and letting it settle, pulling then refitting the indicator at about the 10 o'clock position (trial and error), then lifting over the low end post into the display range. It works for me since 5 psi is about the point the turbo makes itself known and anything beyond 12 psi is gravy

Sixto
83 300SD