The 400 HP 318 specs are here.

One build made 400 HP at 6,150 RPM and 382 lb/ft torque at 4,900 RPM and the other one made 406 HP at 5,900 RPM and 408 lb/ft peak torque at 4,700 RPM. After all of the shouting and hype to sell magazines, NONE of those 400 HP 318 builds resulted in torque figures as high as a basically stock Magnum 5.9 with just bolt-ons:

Mopar M1 single plane intake
Barry Grant Mighty Demon 750 CFM carburetor
TTI headers

The 5.9 produced 345 HP at 4,600 RPM and 426 lb/ft of torque at 3,800 RPM - more torque at an average of 1,000 RPM lower than both 318 builds.

Build a 360. Get a Magnum 5.9 as Patrick mentioned (easier to find) or even snag a 89-92 LA roller 360 block if you run across one. They are probably harder to find than the later Magnum blocks, but all of the later Magnum roller hardware interchanges, plus you have the option of using either Magnum or LA-style heads on it. Casting numbers to look for are 4315830, 53006921 and 53020006.

I will say this, when i was looking for a 360 to build, most everyone said go Magnum, so i found one, then after purchasing it & wanting ideas, most said i should have built an LA, then as you will find out, ALL those magnum heads WILL be cranked, didn't find out this info untill after i made my purchase, not knocking anyone, i'm happy i got it, i do like the fact it has higher compression & a lighter rotating assembly, so thats a plus, but the heads are PURE JUNK, not that they don't flow better, but i will not build (or assemble) an engine with cracked heads period, i don't care if they don't leak, so i threw them away, bought some RHSs from Hughes for 875.00, so plan on another set of heads. Someone did a build on a 300hp 360 magnum, left the lower end stock (the 300hp 360 magnum "crate" has the same components as the production 360 magnum), they installed a cam, eddy heads, & intake/carb/ignition/headers, it made 458 HP, forgot what the torque was, but still, pretty impressive.

Mine should be around 375 HP with a .500 lift cam & RHS heads with the stock bottom end.

http://www.hotrod.com/techarticles/engine/hrdp_0804_small_block_mopar_engine/index.html

here is the magnum build with the eddy heads..etc.

A 30 over 318 with a 4"stroke is 390.6 cid. There is no 360 with equal heads, cam, and compression, ever going to out work it (it's 30 cubic inches smaller). As stated any magnum engine will need heads, and any LA 360 is going to require the same investment as your 318 with the stroke crank. If you build this to the 400 horse 318 specs with the stroke crank you will easily meet your goals and then some. Check summit for the cost of a 318/340 cast 4" stroke crank. Then check with your machine shop on the cost of a crankgrind, add that to purchase price of the 360,and compare your options

Randy