Hi there had the alternator belt go on my stilo abarth, due to being unable to get a replacement stretch belt I had to find a new solution. I sourced a 4 pk 655 ribbed belt ie 4 grooves and 655 mm in length (after a little measuring and swearing lol).
this is my guide also would probably work with a stretch belt
1 disconnect the battery if not be very careful around the alternator
1 remove engine side wheel arch guard and engine side bottom guard (you may find it easier to remove the engine bottom guard. also try to lubricate all the fixing screws inevitably some will break)
2 slacken the drive belt tensioner ( a 15mm ring spanner on the tensionor turning clockwise) and remove belt take note of how it goes around the tensionor etc
3 slacken bottom alternator mounting bolt (this is a nut and bolt awkward to see the nut above the air con pump but you can access it with a short extension bar and socket up the side of the exhaust wait till cool lol)
4 remove top alternator bolt (the alternator is now free to rotate a small amount towards the front of the engine bay and down. therefore slackening the belt take care to watch out for the wires on the alternator do not stretch them undo from clips if necessary)
5 roll off the old belt or cut
6 fit new belt by rolling on.( put the belt on the air con pump with the help of a friend roll on to the alternator its best to turn the air con by hand not too much resistance is felt)
6 refit the top bolt of the alternator by levering with a cut down broom handle on the air con pump and under the alternator and fitting the top bolt (not much pressure is needed and easy to hold in the right place (friend needed)
6 refit the drive belts etc
please note 4pk655 is a good tight fit still has deflection (any belt between 4 pk655 and 658 would suit)
cost £6,55 and several new fastenings lol
hope ythis post helps perhaps if anyone knows how to post this guide in the right place please do it