Help please asap!

Purchase from Summit racing "Trans Dapt" swap mounts for the /6 - 318 swap.
Take the throttle cable, trans kick down, radiator, leaf springs and bottom plate that bolt to the rear end. Some wired may have to be shortened or lengthened.

This will be an easy swap.
They're fairly cheap mounts aren't they?

Even if the '72 has drums you'll want the drums. 9" drums suck and from 10s you can upgrade to aftermarket brakes if you're hung up on an 8-3/4. You'll want the V8 radiator and I'd guess it may be worth swapping the core support if the one in it doesn't have the same width opening. What I'd do is regardless of whether swapping the whole front end or just doing mount adapts I would upgrade to a '73-6 K with discs and an 8.8/8-1/4 down the road. If you don't swap the rear, swap the brakes- it'll be a nice upgrade.