cam for 340 street car

Hi, my name´s Alfred. I´m new to this forum.
I got a 340 in a ´68 Barracuda and want to give it a little more power.
The engine is stock right now, even the cam, except for a FBO e-ingnition.
I plan on removing the heads and doing a valve job and cleaning the ports, and replacing timing gear and camshaft. Wont´t remove the block this time.
The AVS and iron intake shall be replaced by a 750 Holley and Ede RPM intake (hope this will clear the hood). Already have these at home. I´d like to stick with the HP manifolds on the exhaust side.
Car has a TF 727 with stock converter and 3.23 SG rear.
Car is mainly driven in/around town, some stoplight action, little autobahn, "once a year" strip. At all less than 1000mls a year (so mpg and comfort is of less concern).
The engine winds to almost 6000 right now, but without any noticeable power gain over 5000. So after my winter labor, the engine should make power to 6k and gain some extra grunt throughout the rpm range.

As I´m on a budget, timing chain, camshaft and perhaps valve springs are the only things I want to buy (except gaskets...).
I had an eye on the CompCams XE268H with matching springs. Advertised duration like the 340 cam but much more lift.
XE274H would probably need the expensive Mopar chrome silicone springs, because I don´t want to machine the heads for duals. Also I´m not sure about stall and valve-piston clearance.
Bigger Mopar cams like the 280° have single pattern, which doesn´t contribute my intake/exhaust combo. At what size power brakes start to make problems?

Please tell me about your experiences and further recommendations!

Thanks, Alfred

p.s. excuse my English (more rusted than the fish)