Need some help,
I'm restoring a 68 firebird 400 convertible, that is now powered with a 455, how much does the
value diminish without the original engine? Also
do you know where I can find production numbers for 400 convertibles, all I can find is total production numbers for coupes and conv. Thanks

There is no solid number on 1968 400 convertible cars. The estimates come in at around 2000. This is calculated by using the coupe versus convertible percentage. I am no way the final word in this I am sure others can add more details.