Sincere thanks for your help Britt! That's absolutely accurate in terms of the step pattern. These are very rigid however, not lifeless. I have vintage 7.3 Precision shafts in a duplicate set of irons...
The last time I reshafted my mid-80's MacGregor Muirfield irons was in the late 80's or early 90's if I recall. I purchased a True Temper .355 iron set from Maltby with copy that indicated something like...