Here is the GM part number I'm wondering about.

12480034

They sound like good heads, everywhere I read, but everything is either a magazine article, or some other, not always reliable source.

Anyone know if these are vortech style heads?
I guess my other question is do they come assembled or bare? I found them on GM Parts Direct's web site.

I have a GMPP LT4 Hot Cam that I plan on running.

Any info would be great, want to start building an engine soon and have to get the parts selection figured out.

 

These have a combustion chamber volume of 64cc. What motor are you putting them on?

 

A 355

 

http://paceperformance.com/index.asp...D&ProdID=22712
This is the "Phase 3 Bowtie" SBC head. It is not a "vortec head".
It is a conventional 23deg design that uses a conventional intake manifold port location and bolt pattern.
Makes good power especially in ported form.
Most of these heads you'll see offered for sale have been angle milled and will have a resulting, very small combustion chamber. Many, are all used up.
They are popular with the dirt guys.
Unless you already own these heads and they are not mangled, there is better stuff for your purposes.

Again, this is not a vortec head.