It was brought to my attention that the heater box assembly for a 67-69 camaro big block heater core is slightly larger than a small block application to accommodate the larger heater core. This assumption might be as a result of the wide tolerances in the aftermarket heater cores.

Can anyone confirm?

YES!! They are indeed different than the '69 version, and will def not fit properly - I have new repop '67 that is sitting a box! I bought the correct sized version for a '69 from Heartbeat City, and it fell into place.

If you'd like to try using my '67 repop version, just PM me your address and I'll send it to you - if you can use it, we can work out a price. SG.

Some pictures I grabbed off the net years ago.