Junkyard 360 LA Head Porting Questions

I am starting to budget out a simple 360 LA build for my duster so I can know how much money to save. With this, I need a few opinions to help make up my mind. Like the title says, I am getting the engine from a junkyard: pick-a-part, and I am contemplating getting the complete motor (no accessories); $269.00 or just the short block; $195.00.

If I were to get the complete motor, would the stock 360 LA truck heads be worth the trouble porting, polishing and getting milled down? I have heard that the later truck heads crack easily, but I am not so sure they are as fragile as people say.

Or, If I get the short block and pay a little extra for some 340 heads with the same treatment, would the power gains be worth the extra money?

(The end goal for this motor would be to rev to 76-7700 reliably, have 510hp(probably dreaming), and to have 12.5:1 compression(also probably a pipe dream) more like 11:1).

Yes I will have the block blueprinted and balanced, forged pistons, ARP bolts/studs, clevite grooved bearings, and all of the usual oiling mods. I was just on the fence about the heads and the potential power and reliability gains/benefits compared to the price.