I am sure you have considered your need for an appropriate BB trans/mount, driveshaft, etc. Of course, you may want to consider if your systems (ex. cooling, electrical, fuel, etc.) will support the new plant. Take a look at Shumacher for the transition motor mounts.

the K frame is different where the motor mounts hook on between 6 and 8 cyl . will have to change it or modify to fit 8 cyl mounts . radtator and wire harness are also different. rest should be bolt on swaps to 8 cyl parts.big block might need the heavier torsion bars.