De Tomaso installed 650 double pumpers (list 4777) on Euro GTS & Group 3 Panteras. The early GTS/Gp3 which used Q code versions of the 351C actually used the spread bore manifold designed for 4300D carbs by elongating the secondary holes, as you see in 4V's picture.
Chassis 6575 could be a 1974 US Pantera, or a Euro GTS/Gp3. I'm not sure what Mike West has, but the thread title makes it seem its equipped with a Holley.
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