take an estimate, and multiply it by 1.5
you want a strong 400 horse/torque motor? allocate like this: parts will run at least 3 grand if you do your homework for a turn-key; tools are another story. add up all the loose ends and you could be looking at near 5 grand.
maybe you should look into a crate motor? for the cost of all the one-time tools and equipment it will probably just be easier and much less of a headache to buy it finished.