Visually they are as follows

L1 small yellow mixture screw ans 2 fixing lugs either side at the front
L6 as above but larger white mixture screw
L8 no fixing lugs and the white mixture screw
There are 2 types of L8 one pre-lambda which has a red sticker one post which has a green sticker.
P8 no fixing lugs and no mixture screw at all unless you have one of the rare early ones that still had the screw but it did nothing.