GM heater boxes, and firewall fan covers in most cases were universal between most body lines of any given year. Full sized models tended to be more universal then coupes.
The small block non a/c heater blower cover from 69 fits the firewall side of Chevelle, Nova, Chevy II, Camaro, El Camino and Malibu. I also think it fits Firebird, and GTO. However the internal heater box only crosses three lines that I can see right now in the interchange I have access to. The 68-69 Camaro, 67-69 Firebird, and 69-72 Nova all with V8, and no A/C share the same internal box. That doesn't mean that the Chevelle box doesn't fit with slight modification. The Chevelle guys over at Team Chevelle or Team Camaro should have a practical answer for you as to what if anything you need to do to make one fit, in other words if its possible someone over there has already done it and will have the advice you need to complete your project.
