What Alternator have I got please

Hello peeps.
I've got a 3.5 on carbs RRC in my 90.(86 Vintage) Think I may have alternator problems. Whipped it off this morning to get a part number off it,but there aint one.
Looking at the back,it has 2 screwposts and a couple of suppressors which go nowhere.
The Waynes world manual,indicates it's either a 20 or a 25 ACR.

Could someone please clarify model/part number I need. Alternatively if there is a better option,please let me know.

Cheers

if you go on paddocks website and put in the year it will show you the options or give dingo croft a ring and they will tell you.

Cheers Fett.