After some more research
I looked up the 1850 number on Google, info says it is from a 1959 Mercury 383. Anyway, I took off the secondary bowl, (it had an accelerator pump with no actuator arm). The metering block had no power valve or idle screws but it has removable # 72 jets in it. What do I have here? The metering block
has these numbers on it L47772 6501 stamped on it. The list numbers on the
horn are 1850, of course, along with 5752425 and 494. The 1850 is no longer listed on Holley site and the 1850's on Ebay are side hung floats. I will investigate the 3310-1 plates on Ebay. I guess I really need to take apart the
installed carb to get numbers off the plate, to have something to compare.