Our experience with aftermarket CAST cranks has not been good. Most are flimsy and hard to "balance", Scat being amongst the MOST difficult. We tried them in the low-level circle track engines and they simply don't "hold up". The factory crank (400) is a good nodular iron unit. If you find one with no cracks, it's the 'better" casting to use.
If you plan any significant power, the aftermarket forgings are much better. We "like" the Eagle products, but others like Scat. These are both strictly "import". The American-made cranks are very good, and quite a bit more money.
NOTE: Many of the imported cranks are made of CAST steel. Even though they use the word "steel" in the description, these are NOT what we refer to as "steel" cranks. "Steel" implies a forging, NOT a casting.