[donrencos]

It is possible that the block is a replacement for a damaged original. I personally know of one in particular where the original block had both sides punched out by #3 conrod back in the day. The owner/dealer simply got in a new un-numbered block and factory tool re-stamped the correct number for the car chassis number/license records. All this was done within the dealership and was considered to be normal course of events to keep everything legally correct. Given that the blocks were all the same from that period on, there was nothing special about a GTA block other than the number when it was allocated to that model.
I have the original holed block as wall art. (well, under bench anyway)

Same for My Engine. In Brno 1975 a conrod got flying. They continued with a blank spare block (maybe original GTA spec as there are no holes for the fuel pump, so you don’t need the blanking plate). During my Restauration I let the blank block restamp with the original number (Unfortunately the idiot made a „5“ too less). Anyway, it’s well documented with the pictures of the old damaged engine and the change is also states in the FIVA papers. So part of the racing history I would say…