The 'squashed' tailpipe on late SX/GP/dl should be vertical as per the Tutto Lambretta exhaust on the (very beautiful!) SX pictured above. Tutto Lambretta exhausts are vastly superior in quality
and fitment to both Casa and Scootopia. Their GP/dl exhausts come with a 12 month warranty and their S3 'clover leaf' exhausts come with a 24 month warranty. IMHO they are the next best thing to finding a NOS exhaust and roughly the same price as the Casa ones.
Any Tutto Lambretta dealer should have them in stock, or be able to easily order them. Tutto Lambretta dealers include
Travel Lambretta (UK),
STF Lambretta (IT). You can also order direct from Tutto.
The only Scootopia standard exhaust I'd consider would be the S3 'clover leaf' type as it comes
without the internal 'mushroom' baffle, that said I've cut out tail pipes before and rewelded them without issue. As for standard Casa exhausts I had a brand new one that leaked so bad on the roll welded seams that I personally delivered back to Vittorio for a refund. Don't get me wrong Casa make some nice parts, standard exhausts are not one of them.
Very nice SX150! Great restoration. I love small details such as the late kickstart.