Originally Posted by Pre '68 Dave
That would make it a 1955 1st series, 235 Thriftmaster with heavy duty clutch, 3100 (1/2 ton) truck.

F55Q and F55U are 1st series 1955 truck engine codes (this is a large download). The two 1955 trucks specifications manuals are not on the Old Chevrolet Manuals website - they are available at the GM Heritage Center.

Tim,
Did you ID the engine based on casting codes or engine serial number?