2014 hemi 5.7 replacing a 318 in a 1977 power wagon 4X4 ?

There's a big difference between the '03 5.7 and the '14 5.7 . The '03 is a no MDS and no VVT engine. Would be an easier, more basic swap into your Abody. The '14 would be an absolute bolt-in swap to the newer Ram, but wiring harness would be totally different and computers are totally different. So it would be a trade off. Easier swap into the car; lots of issues to work out in the Ram.

Personally, you don't need all the extra features of the '14 Hemi in your A-body. But since you already have the engine, it would certainly be nice. Ignore the temptation to buy the Ram and just keep working on the A-body. Once it's done, you will thoroughly enjoy it and THEN, if you're wanting another project, there will be plenty to come your way. If you try to tackle BOTH of those projects now, it's going to take you more time and you won't be able to enjoy EITHER of them for a longer period of time and working on TWO projects at the same time is really draining on the wallet.