Casting number questions

[Frankie Figs]

I was looking at casting numbers and I noticed one number was used for some 2 bolt main and 4 bolt main blocks. If the cast is the same how can the mains be different? Are the casting numbers on Mortec right?

Thanks,
Frankie

[Brandon]

is this where you're looking?
http://www.mortec.com/castnum.htm

[Frankie Figs]

yep thats it