1966 Barracuda 440 build

My son who is autistic but high function his name is Josh Wooten age 16 anyways he's building a 440 and he bought a very rough66 barracuda we need advice on things he will need his motor is almost done very beautiful Daytona yellow with all aluminum add ons black deep pan and timing chain cover aluminum water pump and housing all he needs to finish the beast is roller rockers and push rods the issue is he's been told what he's doing can't be done and no headers will fit and it will just not work my son is very disappointed he's sees pics of big blocks in 66 barracudas and they have headers all we know is we can get motor mounts but have not gotten advise on anything else he doesn't want to run exhaust manifolds and wouldn't work good with the motor he built but there's so many questions and I need so much info to help him out like I said he's autistic and has had cancer issues and this is his dream to put together his own car he doesn't want dad to just buy him a car he wants to build one his way I sure can use any advice on this car for him and want to get him the things he needs so he can do this please PM me since u seem to be doing whaty son is trying to do thank u so much