I got the idea that just a moderate upgrade was the the idea. It's an American thing to immediately assume anyone wanting to increase their engine's performance automatically wants a fire-breathing 1000 horsepower drag racer. I'm a little different where I can have all kinds of fun all day long with a small block Ford and never go over 5K RPM. Slightly exceeding the speed limit on curvy mountain roads for example.
Back before everybody and his brother had aluminum heads for sale people actually thought well of C9 351W heads. They already have the largest of stock small block valves. They tend to suffer from small exhaust ports mostly. If you stick your finger in one you can feel a big "thermactor" bump right in the middle. C9 heads weren't actually drilled ouit for the thermactor passages though so you can port and polish the ports to your heart's content. And it's highly recommended to do so.
I like what they call an "RV" cam grind. Back in the 1970's they called them "economy" cams. In truth they are both. They are good at low to mid range torque and happen to have a side benefit of slightly better gas mileage. The combination makes for a car that's really fun and responsive during "normal" driving and is also good for a little showing off. These cams have a smooth idle are are not what you want if you are looking for that American muscle car "rumpety rump" sound when idling. Nor good for keeping up with 911's and such on the Autobahn or Nurburgring.
If you're not racing there's not a huge difference between a stock intake and an aftermarket one. That said, I'm very fond of Weiand Stealths for my 351's. Plus a Holley or Edelbrock 600 cfm carburetor. For higher performance racing I like a bigger Holley carb but for street enjoyment it's important not to go with too large a carburetor.
Tr-Y headers have long been known to help with the mid-range torque type performance it sounds like you are after. Not a real big difference from regular "small primary" long tube headers but Tri-Y's are just a bit more optimal. Considering the trouble you may have ordering and (God forbid) having to return headers if they don't fit it might be best to stick with conventional long tube headers that a number of forum members here are ready to swear fit great. Either way, upgrading to a pair of headers and a dual exhaust system I have personally found to also be worth up to 2 miles a gallon and a little actual feel of more takeoff power. Win-win.
I believe in Europe that a 351 (5.8) V8 is perceived to be more of a "big block". And a small block more like a 4.0 liter. But over there generally long-rod short-stroke engines are the kings of the roads. Big and small block terms aren't too relevant where the sole purpose of "big" block engines is to power a large trucks and heavy equipment.
All just my opinion. I also have three motorcycles. A cruiser, a sport bike, and a trail bike. What I do to enhance the perceived performance of one usually doesn't apply at all to the kind of performance I want from the others even though they are all motorcycles. Different folks want different kinds of performance from their cars too.
