Douglas, I was just working on a 69 GMC with a 305, I'm going to scrap. It has a spacer on the Stromberg that will fit your Rochester. The spacer is 7/8 in. high, if that will work for you, email me your address, or you can pick it up. I'm over the hill in San Jose. You can have the air cleaner if you want it too.
Larry
68 C20 327 daily driver
63 C20 292 Camper truck
65 C10 ? Custom Cab AC,PB,PS,$flasher