ryan49, welcome to Bronco Zone!!! The 460 swap is a great mod, and not too hard to do. You'll need motor mounts from L&L Products (available from Jeff's Bronco Graveyard), and a transmission fitted to a 460 or other big block Ford engine. The bolt pattern on the bellhousing of your 351W transmission is different, and there are no "adapter plates" that will work. IT's easy enought though to find a C6 auto or NP 435 from a 460, and swap the engine-tranny all at once. Most 460's will need to have the oil filter mvoed to a remote mount, or nocthing of the front crossmember needs to be done. Take a look at my thread on the 460 swap in my 84 Bronco:
http://broncozone.com/forums/index.php?sho...;460+swap\
The C6 automatic was offered on many engine sizes, both smallblock and big block. Only a C6 that comes from a 460, 429 or 351M/400M will bolt up to a 460. A C6 from a 300I-6, 302 or 351W like in your Bronco will not. You don't really need different springs, since the 460 only weighs about 200 pounds more than a 351W. The only real fitment problem is with headers, since there's a bit less room in the Bronco engine bay. I'm currently using the stock 460 manifolds, and had to massage the firewall a little for these to fit, JSM84