5.7 swap

You are definitely on the right track. The truck trans is the 545RFE and is significantly wider and longer than a 904 or 727. If you are not comfortable with major floorpan cutting and welding as well as fabrication of a custom mount further to the rear than it is better to go a different route. Map63Vette has good advice, but is incorrect about the starter. It is still on the driver side with the 545RFE and TTI headers fit with this transmision. The collector comes within an inch of the transmission pan, but it does fit. If you do some looking you can find many older posts on the topic.
Here's a few:
http://www.forabodiesonly.com/mopar/showthread.php?t=172972
http://www.forabodiesonly.com/mopar/showthread.php?t=164083
http://www.forabodiesonly.com/mopar/showthread.php?t=154422
http://www.forabodiesonly.com/mopar/showthread.php?t=120972

right now power steering is a no go with the factory k-frame, but one box in the works shows promise.