'73 CS with m30b35, 5speed, 45DCOE in San Bruno, CA

On a 3.5 45's would be fine. I had them on a 2.0 M10 and it idled like a watch even with a big cam that came off of an 1800 TI/SA. The key is to build the carbs to the cam, the head and compression ratio. On my M10 I had 40mm chokes and it had an aggressive cam but it also had 13:1 CR. While it was pretty much a race motor it idled fine an felt like a stock 2002 until you hit 3500 rpm and then it felt like someone grabbed tach needle and yanked it over to the red line. The more displacement per cylinder the more choke diameter you need and a 3.5 has 583 cc's per cylinder (16% more airflow than a 3 liter or a 2 liter M10 and 30% more than the 1800), so the displacement is there to support the bigger carb. If you put them on a stock M30B35 then you might want to use a bit smaller chokes than 40mm. 45's can be built with choke (venturi) sized from 30 to 44mm. Choke sizes available are 30mm, 32mm, 34mm, 35mm, 36mm, 37mm, 38mm, 40mm, 42mm, and 44mm. You can probably use 37, or 38 mm chokes for a stock M30B35 and 40's if you had a cam and head work. On a stock 3 liter you would want to used 36 or 37 mm chokes. Bigger chokes give you more high end, but if you aren't turning the motor to 7k or more you aren't going to need them and you sacrifice some midrange drivability.

Nice looking car if was a slick top I'd be looking at it seriously. The bigger motor and the 5 speed are nice additions and it doesn't look like the tin worm has done any real damage.
 
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