my first engine rebuild (318) advises

lol Saab. I guess that's the reason they went bankrupt.

If KB pistons blow the budget, there may be some less expensive help. The stock '72-86 piston sits 0.056 below the surface of the block with the crankshaft at full extension on the cylinder. The 67-69 sits 0.036 in the hole. Some rebuild kits include pistons. Just specify the 67-69 piston when buying the kit. No modifications are necessary.

The 72 piston has a plain flat-top, while the 67-69 has four valve reliefs, as shown below. Good luck with both the meeting and the rebuild.