[KTL]

Those 120/104 cams are nice. Myself and owner of MotoDelta cstreit have them in our 3.2SS & 3.3SS carbed racecar engines. They make good mid and top end power. But on the low end they are pretty doggy. Below 4000 my engine struggles a bit.

I don't think the stiffer springs are a must for the 120/104, as it's not an extremely high lift cam. Not much more intake lift than a 964 cam. However, the 120/104 has a lot more duration which means the valves stay open longer and therein lies the opportunity for valve contact should they float.

ARP rod bolts are typically recommended for the 3.2 or 3.3 Turbo rods with the smaller odd-sized 9mm rod bolts. Stock SC 10mm rod bolts are pretty reliable. I would tend to think the ARPs for street use are overkill. For regular track use, they're "cheap" insurance.