They are manufactured in the same facility as the K-1 cranks.

Exact same material, exact same tolerances, exact same equipment......cheaper price.

The first SB 4.125" stroke prototype seen here in a +.030" 360 block, now 421"

PM Rod (BPE) here on Moparts if you have any questions or you can call me @ 574-340-1966

Rod will be back in town this weekend.