I have this exact set up in my FE. Long story short, you'll need:
1. Modified HR front end - which you can buy already done from Hadfield or do yourself - see
here for more info.
2. Modified floor to fit the box, bits and pieces for this also available from Hadfield and other places. This also entails a proper rear gearbox support.
3. Auto trans cooler mounted in front of good radiator, or new radiator with integrated trans cooler from another model (eg HR), with radiator support panels cut down to suit.
4. Shortened tailshaft to suit powerglide.
5. The p/g dipstick may not suit the FB firewall shape, and could require some rooting around to get right.
6. There are other bits and pieces like vacuum, possibly a mechanical kick-down linkage from carby to p/g that you'll need. If the motor and tranny you've got were previously an item in a HR or HK etc, you should have all this kind of stuff already.
7. All the other requirements of a red transplant to be legal, which varies from state to state. It's been discussed many times here tho, have a look back through the history of this board.
Hope that helps,
RET