I have a 69 camaro original small block car non ac. I would like to change to a big block core and box to move the heater lines over closer to the pass-side fender. Is there an aftermarket kit for this or do I order original equipment to make this change. Also is it necessary to change the inside assembly where the heater core sits or can that altered. I see many pictures on this site that show the lines exiting by the fenderwell and I think it looks a-lot better and will ease with trans-motor changes.

I have a 69 camaro original small block car non ac. I would like to change to a big block core and box to move the heater lines over closer to the pass-side fender. Is there an aftermarket kit for this or do I order original equipment to make this change. Also is it necessary to change the inside assembly where the heater core sits or can that altered. I see many pictures on this site that show the lines exiting by the fenderwell and I think it looks a-lot better and will ease with trans-motor changes.

.........no need to go "aftermarket".Order "OER"(original equipment replacement) parts for you heater box conversion from a company like Ground Up or Classic Industries, BelAir Bob's or FireWheel Classics.

Oh Boy!.....I bet your plans in the future include one big block monster of a motor!

No plans for a big block, just big inch small block. Thanks for the input. I assume the real clean look of a new firewall would be nice but might be a little more then I want to tackle.

The BB core will fit in the interior SB heater box, and you can reuse the SB clips that hold it in. You may need to put a little foam under the clips to make sure it fits snug. Then just buy the reinforcing plate and seal kit for the BB nipples, and use a small hole saw bit to drill the holes in the OE firewall heater cover. The repro firewall heater covers are a lot thinner than OE, and not worth the money IMO. There are threads here with pics and measurements for where the holes go, but they are basically just to the driver side of the crease in the cover, and you can use the reinforcing brace to get the spacing correct.

A good heater box seal kit will include the flat piece of foam you need to glue to the inside of the firewall to cover the SB nipple holes.

I have written posts several times discussing this swap. Do a search in this forum and you should be able to pull it up.