[chiphead]

Depends on if you want a max effort street engine or low-buck chuck. This board tends to go into the "full $5,000 rebuild" mode every time somebody comes in here with a stock 400. By the time you get dish pistons, forged rods, machine work, expensive valvetrain parts, etc that are recommended for a street/strip engine, the bill is 5 grand plus. By then you realize you could have a real engine with a stroker kit and aluminum heads, so the total project snowballs to 7 grand.

For low buck, take that 400, give it a set of rings/bearings, oil pump and cam/lifter set. Reuse stock rods/pistons if bore is still within service limits. Throw a set of 90-100 CC heads on it and let it ride. Look for 6X-4, 5C-4, 4X-4, 96, etc heads from '72-76. It'll run on 87 octane, be easy to tune and dead reliable.

You could build a basic 400 like that for $1500 in parts/labor. It would make an honest 350 HP pretty easily. Just don't revv it over 5200 and it'll live. Save up and build a more powerful engine later.