it can be done at the same time.make sure the you are at top dead center before you tear down.also the repair book says to line up marks on the bs chain but if you do the bse then it dont matter just make sure to put the smaller chain on and the oil block off ring for the upper bs spot.i have done 4 of these it is pretty easy if you have ever done a timing chain before

87 dodge power ram 50,35" tires,5 1/2" total lift,4.6 gears,lockers front and rear,Rancho RS5000's,custom front bumper,custom rock sliders,cct extended diff breathers,75 amp alt(40 amp stock),thorely header,K&N,wheeled hard...