There is no listing in the GM parts catalogs for 1970 SS 350 Camaro or Chevrolet Pass Car 350 with 4 Barrel Carb anti-diesel solenoid bracket
The idle stop or anti-diesel solenoid bracket with Quadrajet 4BC is not listed in the 1970 Camaro Assembly Manual or in the 1970 Chevrolet (Impala) Assembly Manual and is not listed in listed in Group 3.444. in the Chevrolet Parts and Accessories Catalogs dated 1970, 1971, 1972, 1973 or 1974.
I can't find the 1970 style Quadrajet 4 barrel carb solenoid bracket listed anywhere in my GM smog books, 1970 Service Repair Manual or in the 1969 Chevrolet Parts catalog dated July 1969. The 1969 Chevrolet Parts Catalog lists solenoid brackets for Q-jet's with 4BC and Holley Carbs and mounts with a bracket and clamp like the one used on the 1970 Z28 with automatic transmission and do not look anything like the 68-70 style bracket I have.
I have an anti-diesel solenoid bracket for Quadrajet 4BC purchased thru a business that only sold smog parts over 15 years ago. The 1970 style bracket uses the small center screw on top of carb and the long 5/16 bolt (carb to intake mounting bolt) to mount bracket to carb. I am not sure if this is even a GM bracket, this may be an aftermarket bracket sold thru auto parts stores to stop dieseling problems on 1968-70 style 4 Barrel Q-jets. Aftermarket companies made replacement solenoids and may have made this bracket too, if there was large enough call for an item like this.
The 1970 Chevrolet Parts Catalog and 1970 Camaro Assembly Manual shows only the 307 anti-diesel solenoid bracket and the 350 with 2 Barrel Carb anti-diesel solenoid bracket (different than 307) and No listing for Chevrolet Pass Car (Impala) 350 with 4BC anti-diesel solenoid bracket and do not show idle control solenoid bracket to increase idle speed for A/C equipped Cars.
The 68-70-style anti-diesel solenoid bracket I have is bare steel and has no part number stamped on the bracket. GM solenoid brackets are gold plated and are usually stamped with a partial or complete GM part number and the company's logo.
1971-73 Quadra jet solenoid brackets are gold plated and stamped company Logo "BP" and 42682, the last 5 numbers of the part number and are listed in Gr. 3.444 Bracket Carb Solenoid 7042682 with Roch. 4BC
1971-73 style brackets use one slotted tab on the front and another boxed type tab on the side of the carb (tabs are casted on 1971-73 Q-jet 4 barrel Carbs) and a screw on the front of the carb for mounting the bracket on 4 barrel Q-jet Carbs
The pics below show the 68-70 style bracket vs the 1971-73 bracket
Not sure if this clears up the question or causes more confusion, but there is no listing for 1970 anti-diesel solenoid bracket with Quadrajet 4 barrel carb.