Rebuild 915 heads or go aluminum?

Hey guys, got a few questions.

I recently stuck a 440/727 into my Duster. It runs and drives good, just doesn't have the power I thought it would. I am almost certain its a later year block, and I will verify when I get home tonight. With that being said I think its probably low compression motor. I am going to check cranking compression and leakdown test tonight as well.

After some digging around I found that the 915 casting heads are the most desirable stock head at least if you want to bring up the CR. Talked with my dad and just so happens he has a set. They will need to be gone through and freshened up.

My question is, is it worth the $$$ to rebuild the 915's or go aluminum now? Also should note that I am going to put together a good bottomend from parts we have around. 67 or 68 block, couple different crankshafts to choose from, good rods(cant remember brand) and have some KB10:1 pistons and have some speedpro (I think) 11:1 pistons. Would be buying a camshaft that will work with whatever we decide to build.

Any advice would be greatly appreciated!