What is the smallest stock battery group size for an '87 GTI 16V? The gti16v.com specs only says this for the battery:
12 Volt, 54 Amp/Hr. (63 Amp. with A/C)
I've currently got a huge group 41 battery, it supposedly weighs 34.5lbs. The alternate batteries that Napa lists are the group 48 and 91 at 36.6lbs. The group 90 battery in my 2001 Focus is substantially smaller...... So I want to see if there is an allowed stock replacement that is smaller and lighter than this huge group 41.

So how do I find out what is the allowed stock size replacement batteries to see if I can shed a few pounds here? (I'm thinking one of you has already done this research, so I'm hoping someone can share. )