I'm in the middle of replacing the alternator on my 156. I decided to go the "official" route from below rather than disturb all the intake and throttle gubbins on top.
It may not have been the best choice
because you have to remove the front exhaust section (the studs will
be corroded), disassemble half the off-side suspension, unbolt the drive shaft and remove the intermediate shaft, amongst other things. All bolts will invariably be very
tight and aluminium components will be corroded on to the steel bits!
I have a generic (small) 3/8" socket set, so no deep sockets and no long extensions. Most things I could fudge around but when it came to removing the intake manifold mounting bracket from below I really needed a long extension, something in excess of 12" as there isn't room for a ratchet in the space below the manifold behind the engine.
I went looking for decent quality extensions and was horrified at the prices!
Then I came across this: Sealey AK6356 - Adjustable Extension Bar with Swivel Head 290-430mm 3/8Sq Drive at PVR Direct.co.uk
If you sign up with them you get an introductory offer which can be free postage or money off.
I used the extension today and it made getting those bolts out really easy, particularly with the swivel end since the path to the bolts isn't straight.
Also I've read of people having a problem getting the intermediate drive shaft out. Me too! It didn't want to budge with the usual persuasion and I've heard some people have chipped the end off a crowbar trying to lever it out; besides levering against an aluminium bracket didn't seem like the best idea.
Enter the slide hammer that's been unused in it's box in my shed for years; 5 minutes of phaffing to get it adjusted up and aligned, 15 seconds later out came the shaft closely followed by 1/2 litre of gearbox oil!
Anyone else got any tales of really useful tools?