Les,
do you recall who makes the headers for that chassis? I purchased a Daytona that's been back halved and am currently fitting it for a small block.
@pittsburghracer used to have a Daytona with a small block, he might be able to help. However, depending on the front suspension, and inner fenders, I think you will need a custom set of headers.
If you're something of a gambler, you could try a cheap set of summit or jegs headers, and plan on moving a tube or five, till they fit.
Considering top-shelf headers (TTI, Dougs) are nearly $1000, custom made around $1500 is probably not a bad deal, IF you can get em made for that. (I'm cheap. I'd try a summit set, and buy some extra bends and fire up the welder).