Thomas - The block casting number "3836233" I show listed as for 1955-57 235's with the low mount (large casting hole) water pump location. If the plan is to use this later 235 in your 1949 3600 (I had to go back through your old posts to try and figure that out
), the engine and your truck will benefit in the cooling department by getting and installing one of
Pre '68 Dave's water pump relocation kits to get the water pump and fan back into the best spot for your radiator.
The "F55Y" in the serial number confirms it would have been originally installed in a passenger car equipped with the Powerglide transmission as you surmised. The original compression ratior listed in the GM Heritage files says "7.5-1". Betting Jerry (HRL) will chime in here on what you can do to achieve that compression ratio increase.
