700R4 GM in a Swinger?

Here's a post of mine from a year ago along the same subject but using a 200-4R instead of the 700-R4:
I've been thinking about a 200-4R behind a 360 magnum crate motor in a '69 Dart for the past week or so. Talked to several tranny companies about it and finally contacted Art Carr at California Performance Transmissions last week. He estimates total cost including converter and installation at about $3300. This does not include a new 8" longer driveshaft since the 200-4R is 8" shorter than a 727. It's also lighter and doesn't have as much HP loss through the transmission. The gear ratios are better than the 727 and it does not require trans tunnel surgery to fit. Art says he has a customer in PA with one behind a 406 stroker that runs 11.80s and still pulls down 25 mpg on the freeway.
Somebody tell me something bad about this setup......

Nobody came back with anything bad except the standard "Don't put a GM part in your Mopar". I haven't progressed enough with my project yet but still strongly considering this.