IF you check the casting number lists, there is ONE casting number that was used for 413 AND 426 industrial engines. There are, I believe, other industrial 413 casting numbers and industrial 426 casting numbers. AS WITH ANY MOPAR CASTING, let the sonic checker tell you the answer. That "underbored 440" crap is just that, crap.

The problem with 413s is that they should be free engines, the same as 318s and 361s. But give a novice a "bigblock Mopar" engine and he'll think it's gold. Those motorhome 413s show up on Craigslist for $800, makes me puke. Now if they were priced right, they might be interesting. But a 360 with a 4" crank and decent heads will outrun one in the same car.

R.