Mr. Wood - welcome!
There are MANY suppliers of parts out there that can provide you with all the chassis stuff you are looking for. It all depend on how deep your pockets are. The best thing to do is use Google to search 56 chevy truck front suspensions and find what you are looking for. Click on the "Shopping" tab and that will usually pop up at least 10 suppliers with the same product at all their differing prices including shipping in most cases. Choose the one you want and get out your card! Its really that simple.
Some of the top suppliers to get yourself really started are:
Art Morrison
Chris Alston Chassisworks
PB
No Limit
TCI
Fatman
For MII fronts there are many manufacturers too:
Helix is probably the most common
Heidts
all of the ones above have their own versions too.
good luck on your build.... start a build thread!