I m no engine builder ,
I do believe aluminum head require different studs weather TA or GN1 (I had a set of ARP for irons)
Push rod length changes ( I had a set )
TA SI can use stock rocker ,GN1 I don't know (I had a set of TA rollers )
I got a good deal on a Champion Intake ported for Irons
For me Irons were $ effective with only 11.5 ET target
I may have spoke out of turn ,Tom was trying to sell me what I need not what I wanted (Aluminum)
I was going 11.8 with parity much stock head and CR ,and cost for a locale machine shop to fresh-ion them up was a lot $
TA performance have been super people ,I have a lot of there parts