Magnum 360 heads "best" for my build?

So I have a set of Magnum heads ready to bolt on. After some careful consideration looks like I can do about a .510 lift with the right springs.

Considering the XE268H cam http://www.summitracing.com/parts/CCA-20-223-3/

Block is a .030 over '99 magnum.

Will be going into a '71 Scamp in place of the tired 318 in there now.

Rear is 2.76 geared, thinking about 2.94s, 3.21s or 3.55s, but fwy cruise rpm is a concern

Trans is a 904 with stock converter, upgrade pending based on overall build

Car will be street/strip driven, 85% street, spirited driving

While I know I can drop $$$ on heads, will the magnum heads suffice?
Should I consider doing any work on them?
How can I expect the car to perform with these heads and Hooker Super Comp headers?
Would 340 manifolds be better?
What would be the overall compromise in performance running these heads?