Re: Is this a Big Block Car?
The firewall is the same on both the big block and the small block. Having said this, when converting to the BB heater core and cover, a rubber seal is supposed to be installed between the internal heater core box and the firewall. This seal covers the two holes normally used for the SB. Hard to say if its real based on your description, but some insulation poking out of the firewall does not mean that its necessarily a clone. The owner could have neglected to install the seal, as it can be a real PITA to install at times. One might ask why the core needed to come out though, because if the seal was missing, it may be have had a core recently.