Post the castings codes, date codes, and engine serial number (a photo of this, if you can).

Most likely that block has solid/mechanical lifters?

0996855 F5 -- does not match the format of Engine Serial Number sequences in Specification Manuals.
Let's see a photo - maybe it has been added/changed?

You info is correct regarding the date range of the block/head (1953-55 Corvette 235 and various car/truck 1954/55 235).

Casting & Date codes will confirm a lot of speculation.