1 9 6 0 ▁until ▁ 1 9 7 8 , ▁when ▁the ▁New ▁Look ▁was ▁replaced ▁by ▁the ▁" 8 7 0 " ▁Advanced ▁Design ▁Bus . ▁Over ▁its ▁ 1 7 - year ▁production ▁run ▁ 1 3 , 1 2 1 ▁Fl x ible ▁New ▁Look ▁bus es ▁were ▁manufact ured . ▁ ▁Design ▁The ▁Fl x ible ▁New ▁Look ▁bus ▁shares ▁many ▁design ▁features ▁with ▁the ▁G M ▁New ▁Look ▁bus ▁that ▁was ▁introduced ▁in ▁ 1 9 5 9 , ▁however ▁the ▁Fl x ible ▁New ▁look ▁bus ▁was ▁somewhat ▁more ▁rug ged ▁and ▁solid . ▁Both ▁bus es ▁featured ▁large ▁ 6 - pie ce ▁" fish bow l " ▁wind sh ield s , ▁forward - slant ing ▁side ▁windows , ▁fl uted ▁al umin um ▁s iding , ▁and ▁slide / g lide ▁front ▁passenger ▁doors . ▁Both ▁bus es ▁were ▁also ▁equ ipped ▁with ▁the ▁same ▁engine : ▁the ▁Detroit ▁Dies el ▁ 6 V - 7 1 ▁( 6 - cy l inder ) ▁/ ▁ 8 V - 7 1 ▁( 8 - cy l inder ) ▁dies el ▁engine ▁( how ever , ▁ 1 5 0 ▁prop ane - f ue led ▁Fl x ible ▁New ▁Looks ▁were ▁built ▁for ▁the ▁Chicago ▁Trans it ▁Author ity ▁in ▁the ▁mid - 1 9 6 0 s , ▁Detroit ▁Dies el ▁ 4 - 7 1 ▁( 4 - cy l inder ) ▁dies el ▁engines ▁were ▁available ▁for ▁some ▁models ▁in