Hi guys - I'm new here!

My pride & joy is a 1968 Iso Grifo 7-Liter, which for those who are unfamiliar, is an Italian 2-seat GT, using good old US V8 muscle. Most of the 412 built were 327-powered, but there were also some 350 small-blocks, and later on, Ford 351C. Included were 90 built with Chevy 427 or 454. They are great-looking cars, and can hold their own with contemporary Ferraris, Masers and Lambos.

I have just done a major rebuild on the engine, and generally, I am really happy with it. It gave 463hp at 5400, and 522ft lb at 3800 on the dyno.
The rotating assembly is all good stuff - forged crank, 4-bolts, Manley H-beam rods, forged 9.8:1 slugs, steel flywheel, Fluidampr - so it can take plenty of hp.
Heads are Edelbrock Performer RPM, fitted with Comp Cams beehive springs and titanium retainers (to try and beat valve-float with hydraulic roller). Carb is a Holley 750 double-pumper massaged by Chuck Nuytten of Dallas specifically for this engine, and am told it will flow up to 890cfm. Exhaust is custom stainless long 4-into-1 headers with twin 3" pipes and mufflers (sounds awesome!).
We can get 97 octane over here in England, but over 7 bucks a gallon - ouch!
Gearing is very high - 2.88 rear end with Super T-10 4-speed with a 2.88 1st gear. This car needs to top 170mph (in Germany, of course!)
However, I am very tempted to try a Tremec TKO600 5-speed with the 0.82 5th ratio and a 3.31 axle. I reckon the gearing would be about perfect then - decent acceleration and high top end.

At the moment I have a Lunati hydraulic roller, fairly mild with 218/226 @ .050", 112 deg lobe centre, and .534/.544" lift.
I feel the engine isn't as eager above 4000rpm as I would like. I would like it to feel as though it wants to race up to 5000+ rpm. So, I would like to raise the torque peak to about 4100 and hp to say, 5800.
My question (finally!) is: would a hydraulic roller of 230/236 deg @ .050", with same LC and .547/.547 lift do the trick?
I would be pleased to get nearer to 500hp, and realise the torque would probably drop to more like 500ft?

I'd be interested to hear any views!!