u/Horror_Swordfish_700

Hi all, I just picked up a force of Iron Hands the other day, and I want to add some Gorgons. With the new Horus heresy Terminators getting a size increase, i wanted to know if it would be best to get the old 40k Indomitus armour or the new ones?

I know i can get the FW models, but I like custom making my models, so I want to know which of the base models I should start with? Thanks in advance