2.9 Head casting #"s

[Rangermessenger]

Machine shops in my area are busy, weeks out on getting my heads checked out, I was thinking of going with one of the online head exchange sites. My question is the casting number on my current heads is 21030 (I have read that this is the head that is prone to cracks) I also have read that there is an improved casting, does anyone know what that #number would be? and how do I make sure that's what I get when I order?

 

[rusty ol ranger]

Im not sure the actual numbers but...

Casting TM86 (86-88) 2.9 heads are the crack prone.

TM89 (89-92) ones are the improved.