There have only been three different front intake K&B .40s over the last 36 years. The first one has a small front ball bearing and was produced until about 1979. The second generation has a larger front bearing but still used an aluminum piston with a Dykes ring. About 10 years ago K&B came out with an ABC K&B .40 that had different porting and a tuned muffler. This is what MECOA now manufactures and sells.

As a side note, K&B also made Rat Race and Formula 1 K&B .40s with a rear intake from about 1966 to 1973.