hi scott
i recently had one of those
from what i recall its not that easy to use in a rod application, the original intent i bought mine for , but learned of the difficulties, so i resold it
it is based on a chrysler 354, but the heads are different along with the waterpump system
yes, all of the parts are available to convert from either hot heads or PAW
but any and all parts needed for the early hemis are very expensive, by the time i was done pricing the items needed to make it usable in a street rod with some mild hot rod parts, it was very expensive, like over 5k in parts alone, not including machine shop work
the valves in that motor are sodium filled and need to be replaced for use, valves are very expensive too
a member here trwaters is into those and makes some parts for them
i think the trans adapt kit is close to $400 alone
its easier starting off with the 56 chrysler motor you have, but still expensive, i believe thats the first year without the built in bellhousing to the block, so thats easier to use
but that 57 dodge truck is just one of the more costly ones to hot rod
i believe it should have a 2bbl motor with a governor on it
you can call hot heads, they are very knowledgible and helpful, but parts are expensive
good luck