I ran a 1050 on my small block with down legs. Went mid 10's @130 through the exhaust 3650 lb. street car. A straight leg carb didn't work for me at all.
1050, I like it. build the engine to work with the carb. :D
I have a sweet spot for the 1050.
I don't think I'd mess with an 850 on a 318, I'd lean more towards a 650.