Volvo Repair: Timing belt, idler pully, cheap insurance

Question
E.
My 1999 V70 has 104,500 miles on it and I am going to replace the timing belt.  Do you recommend replacing the tensioner, idler pulley, and water pump at the same time regardless of condition as relatively cheap insurance?  Also, which parts need to be Volvo and which can be OEM or aftermarket? I saw an Aisin OEM pump that was half the cost of the Volvo pump.  Thanks in advance

Answer
replace timing belt and tensioner the tensioner brakes before belt  you don't need idler pully if is not bad  watter pump you don't have to  change but is recommendable  you can do it it will safe you labor money in future if it goes bad .stay only with original Volvo parts  they will less much longer than aftermarket parts .