Well, it is going to be a fun project to say the least. Time to break out the tape measure first, mostly in the firewall and transmission tunnel areas. Next concern is the oil pan, but there should be something available, new Hemis in B bodies and trucks have to be available so not that big a concern, otherwise it may need altered a little bit for the K member of the truck but shouldn't be that big a deal. Next is the electronics and transmission, it all needs to be swapped in unless you go standalone aftermarket, that will be fun mostly in trying to remove components you don't need, which are few, a body control module for door locks, etc., may be tied into the main computer. Sensors and gauges are a fairly easy wiring swap. Motor mounts should be available aftermarket, look for Hemi swap to B body big block, they should be available, same with trans mount. Lastly is exhaust manifold clearance for the frame rails which, that may be a small issue, but that's what the tape measure is for, so headers may be the only solution for that if they don't clear. Drive by wire gas pedal shouldn't be an issue to deal with. Other than that, sounds like a very fun project.