If you're going with Chevy 63's the front spring hanger (bolt center line) should be 11 inches forward from the stock hanger position. This should place your rear axle in the stock location. Then you can place those rear hangers pretty close to where you have them positioned in your pic...maybe slighty rearward more depending on the shackle angle you're looking for. 
thats about where i have the one side placed, once i get the other side tacked in ill put it together and see what my shackle angle is.
OH! Almost forgot... for the best (and cheapest option) also use the stock Chevy 1/2T U-bolts and spring plates as your U-bolt flip kit. The bolts are 5/8 and fit the Toyota axle perfectly. The U-bolts are bigger than any other option out there for this. 
actually the cheapest option is the free ones i got from dave haha
not sure exactly what they are, but they seem to be bigger than the ones i got for the front ubolt and plate wise.
let me know if ya want someone to watch ya I get bored LOL
i may need help getting the new springs in position, i think i have 4 leafs, so ill have to remove a leaf, but i cannot remember off the top of my head if its 3 or 4.
