I would strongly recommend visiting the 385 series engine forum at
www.460ford.com and asking there if there is a seasoned and knowledgeable builder in your area, and work locally.
Why?
Engine shipping is expensive; and considering that if you have ANY problem with ANYTHING, you will need the aid of a local builder anyway...any mail-order company can't help you until you return the engine; which means removal from the vehicle. You are much better served to get a local guy to craft you something locally; and take responsibility for it locally.
Aside from that, there are guys out there that can far surpass the bang/buck value you're looking at with the other builders you're considering.
Hopefully there is a godo builder right in your area; that would be ideal.
Byron