L2348F is the forged 351C piston with a 12cc pop-up dome originally manufactured by TRW. I don't know if TRW exists any longer as a business in any capacity, but they haven't manufactured automotive pistons in a long time. Federal Mogul evidently purchased the rights to manufacture the old TRW line of pistons. Federal Mogul is the parent company of Speed Pro, Sealed Power, Fel Pro and several others too. The L2348F pistons are actually sold by Sealed Power now, and you'll usually find them sold as Sealed Power/TRW.
Caution however ... I believe Probe industries also sells a rip-off piston with that part number.
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| 351C Technical Information
If you use a 351C 4V powered vehicle for a grocery getter ... the eggs aren't going to make it home!