Ok, technically the donor in this case was a Mark VII, but I couldn't pass up the title. Check out this cool little article on installing a Ford 5.0 in a RX7.
http://members.tripod.com/~grannys/1stgenfordefiinstall.html
I must say that is very cool,the weight to power ratio on that has to be Crazy.
i did one of those about 6yrs ago to an '83 rx7 gsl. never got it running though. all i had left was a fuel system to do, and it would be driveable. it had a '91 crown vic 302 and a '81 C4.
i made my own tranny x-member, and had the stock driveshaft cut down, weld a standard size yoke on it, and a metric-standard u-joint. it would have been a lot of fun, had i finished it. i still think about giving it another shot, but the t-bird gets all my time and money now.
(http://www.mustangmods.com/data/14489/picture_011.jpg)
(http://www.mustangmods.com/data/14489/picture_012.jpg)
(http://www.mustangmods.com/data/14489/picture_009.jpg)