Only ever had one fan belt issue on my 1985/6 +8 and that was while attending LM circa 2002, when in the company of Porsches and in hot weather I was pushing on for quite a bit of the day, and on my usual morning checks found the fan belt to be in a somewhat threadbare state.... Fortunately I ever carry a spare, and the tools to replace it having taken the time to ensure I have just the right spanners to complete the task by performing a dummy run.... Which really was a dummy run, as it was pointed out to me having completed the task and sharing how I went about it, someone in the forum ( eMog or MSCCDG )politely pointed out that there was an access slot cut out of the inner wing to ease the access to the alternator adjustment bolt....Whereas, I had gone about it from under the bonnet... Duh...!
Fan belt for my mid 80`s 3.5 +8 with standard Lucas alternator GATES 6225 MC AVX10 x 1125 La
Back in time the guys in the MT dept reckoned Gates were good quality belts, though that was a long time ago, and applying old thinking after years of downsizing, delayering, and off shoring, who knows who owns any company these days and the way standards might have altered...?