John
Guest
That depends, what throat series you have got on the N7IJ Early_short throat limits you to 300 series and 20' to 24' are good sizes. Or the late_long throat, then almost any series head will fit 300 and newer. Early throat has a narrow hook on each top corner and late throat have wide hooks the on each(put together cover between 1_3 to 1_2 of the top of the throat) at each corner. The main drive belt is 10" longer on the long throat. My 82 N6 S3 has the long throat and parts manuals for that serial n call for the short throat. The long throat will run with the new heads with very minor changes. Hope this helps!