If pistons are the same sizes for bore, all 3 rings, pin diameter, etc - what effect does a different set of dimensions for the dish have on the engine?

• Dish top 0.305" deep x 2.460".

Dish top 0.330" deep x 3.130".

 

Increase displacement, effect flame front pattern, allow clearance for different valves, possibly changed / improved materials....

 

So if the stock pistons are the bottom list, then the pistons from the top specs would not be a good option. Appreciate the info.

 

I sure don't know what list you're looking at but I'd contact the company which put that list together.
People who change pistons / rods know what they're doing and almost ALWAYS are copying a project someone else had already done.
Do what you want but I wouldn't change pistons in a stock engine except if one or more was damaged. Even then, with a stock engine, your choices will be limited.

I've touched pistons in one rebuild in my life. The owner had a great recipe, bought all the parts and I was just additional hands.

 

I decided not to change the pistons because none seem damaged. But how do I clean all the existing carbon buildup off them before reinstall?

 

After you remove the heads, turn the engine so the pistons (one-at-a-time) are as high up as they'll go; flush with the block.
Get out the wire wheel and your drill.
Lots of guys post that they've looked into the cylinders with a borescope and decided to do "piston soaks" in cases of severe buildup.
This is an "add product and let it sit" process. Berryman's makes the carbon solvent they all use. It's all about softening the stuff.
Freeing up stuck rings is also 'promised'. This all takes time and reapplication. I've never done it but there seems to be a consensus on doing them (piston soaks) in aged / neglected engines.