There is absolutely nothing wrong with a 400, they are actually preferred over 440s for stroker applications. They generally have more meat in the lower end than a 440, a stiffer, lighter block, easier to fit in an a body.
The reason they had a bad reputation was the factory versions had no compression (really around 7 1/2 to one), no camshaft to speak of, smog tuning, and detonation because of no quench, piston way down in the hole.
Non stroker 400s can still be hard to make run well, there are virtually no decent compression pistons available, short of a custom high-dollar forged piston. There is FAR more good combos available as stroker kits. Putting money into a 400 without stroking it isn't cost effective.
