Yes you can take them further than an ICH head... they have NO water jacket under the intake short turn, you can push the ST into oblivion (generally makes head flow more) The set I have pics of on my site has almost NO short turn, whoever ported it just killed it, so much so, the seats were starting to pound their way down into the ST because of a lack of stability. Yours do look like a nice casting, you can tell how good the alum quality is by looking at the "shine" on the machined surfaces. Most of the ones I have seen have been porous & soft. I think yours were definitely a later casting.... I have a Virgin set of Arrington heads that are similar, VERY very nice quality castings, but most Arrington heads are soft & porous. (Arringtons were cast at Diamond as well)