Old Mahle pistons are +.030 overbore and came in at 515 grams. After an unscheduled disassembly, I had to go with +.055 pistons that are exactly the same save for they weigh 525 grams. Is this enough of a difference to worry about?

That (10 grams) is almost 1/4 of ounce, correct Then times 8 on the wrist pins, correct I wish I had an answer but I don't, sorry
How confident are you that you can do some careful weight removeable to the new ones to match the old ones?

I bought the hemi build book from Richard Nedbal. He was and engineer from Ford for years. He’s pretty smart. He made a comment in his book about balance. I’ll try and remember the quote but I left the book at a friends house. “ 5 grams out of balance on a 4.500” bore is equal to 100 lbs at 7000 rpm”. That seems like a lot of weight slinging around that should make some difference. I know that I’m working on a hemi build right now of a motor that has been put together by someone who knew very little about precision engine building. They used a max wedge crank with the factory balance, hemi rods and heavy TRW 12.5 pistons. The owner told me he mixed AVS gas and premium when he put gas in the car. He did not put many miles on the car on the 25 years this motor was together. Probably between detonation and the out of balnce, it beat on the mains caps. Three and four caps are loose in the block to the point you can wiggle them.

I thought about removing a little but realized that the originals lost weight off the coating of the skirts and some carbon off the tops (I cleaned after removing).

FWIW (and I just read this for the first time myself) - https://www.enginelabs.com/engine-t...1-battling-primary-rotational-imbalance/

Have the new pistons lightened on the bottom

That is the direction I was headed.

10 gr on the recip isn't a big issue, my 2c

I took a paint scale and took weight off my new pistons to match the old ones. I have even welded on some new one to add a little weight to a set I had the was too light one time. I've used that old paint scale for a lot of things through the years.

10 grams of piston weight wouldn’t concern me a bit…….as long as they’re all about the same.
One piston 10g off, I’d try and even that up a bit.

10g is .353oz.

10 g on the piston is nothing to worry about

Thanks, guys, I appreciate the feedback!