350 hp from a SOHC, YES its possible. The SOHC's bottom end is actually stronger then the OHV's because it comes from the factory with a girdle built into the oil pan. I'm working with this to bolt onto a early style OHV 4.0 as well.
The SOHC heads outflow the OHV's as well, ported they can achive great percentage numbers as compared to intake and exhaust ratio's. Near 80% intake to exhaust flow ratio.
As for now there aren't any new core's available for the camshafts but they can be reground. Not very good as the camshafts are actually pretty decent in stock form and require a great deal of mechanical knowledge to interchange.
Now in order to gain these kinda numbers you will have to add some form of forced induction. Wether it be Nitrous or a supercharger. Also make sure you have all the other bases covered, like mild bolt on's. Headers, MAF, and free flowing exhaust.
Finally get it custom tuned by a 4.0 knowledgeable chip tuner like Brian at Apten and I'm almost positive you'll get what your looking for.
On a light note, here's a picture from some of the beginning stages of a Paxton SN-series supercharger that a friend and customer of mine has installed. He's having the head unit rebuilt as we speak and should have it back together this weekend. It also has the better flowing impellor wheel and the paxton cooler, Coupled with achol injection for detonation supression and a custom tuned Apten chip we're headed to the dyno probably next friday. With a similiar setup, using an Eaton MP90 on a stock SOHC with no chip tuning we made 247 RWHP and 290 FT/lbs of torque at the wheels. Given that this one has a chip and a more aggressive S/C we should be a bit higher hopefully.
We'll see!!
Later Doug904.
SOHC with a Paxton picture.