Base part number 3. Suffix if applicable (WR = rings installed or ha = hard anodized) 4. Oversize designation For example: 224–3512 ha .030 The order quantity is now one (1) so you should order the exact quantity of pistons you need.
https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs-&-thumbnails/catalogs-and-literature/pistons-and-rings/pi-20-09.pdf
This catalog contains pistons for domestic and imported passenger car and truck engine applications and contains several significant changes to the part number system and order quantity procedures. The part number is completely new to accommodate the integration of the mahle Original®and Clevite piston programs.
https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs-&-thumbnails/catalogs-and-literature/pistons-and-rings/pi-20-09.pdf
9= Ring groove widths 10= Piston pin diameter 11= Compression height 12= Piston pin hole location 13= associated piston rings 2 | © mahle 2009/2010 1 2 3 4 6 7 5 8 9 10 11 12 13 How To Use 1 2 3 4 For technical service call: 1-800-248-9606 Hours: 8:30 am - 6:00 pm EST (Monday - Friday)
https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs-&-thumbnails/catalogs-and-literature/pistons-and-rings/pi-20-09.pdf
Platinum Pistons Incremental Sizes Custom Platinum Series Pistons The ordering process is as simple as 1 - 2 - 3 ! 1. Select the catalog part number you wish manufactured with the singular exception of the final bore size. 2. Tell us the bore size of your block.
http://www.manleyperformance.com/dl/cat/pistons.pdf
pdf for "old trw piston part numbers".(Page 1 of about 17 results)