I went with Ives' original choice of Gran Classico and paired it with Tempus Fugit Alessio Rosso. This was excellent and came across more as a Boulevardier variation than a Manhattan variation; there's just so much more going on than one typically finds in a Manhattan. I wonder if TF Alessio Rosso Vermouth has enough wormwood that Simon would classify it as a vermouth amaro? It doesn't appear to be listed as such in Difford's Guide.
Thanks, Chris. I've added Alessio Rosso Vermouth di Torino to Difford's Guide as a robust vermouth amari based on your comments and others online (It's not yet available in the UK for me to sample.)
I love Carpano Antica, but if you don't have it I find that replacing 3cl Antica with 2.5cl red vermouth and 0.5cl Licor 43 and dashes of demerara syrup to taste works surprisingly well. That's what I did in this cocktail and it worked very well. It's overall a slightly sweet Manhattan, with pleasant mint and cola accents from the amari. The Fernet is always going to make itself known in cocktails but I didn't think it was overpowering by any means.