I asked a Bonneville guy (Scott Cook) with a nearly completely redone SC 3.8 about the forged rods and this is what he said:
According to Richard Lee [builder of the Spirit of Bonneville, Salt Flats car], several companies will custom make forged L67 connecting rods.
I stuck with modified stock connecting rods, because Richard Lee felt they would be good to about 530 horsepower.
Hope this helps!
Scott
97.5 GS