81-83 vs 84-85

Can anyone out there explain to me why an 81-83 720 will lay w/o spindles but an 84-86 have to have them? I know I'm drawing straws here but...

my 85 lays engine xmember, or did when it was first bagged, now the xmember is drug flat from nose diving... now its a 1/2".
just had to notch the frame some for the LCA to come up. oh ya they are only 16s dunno what your running