went over to my friend's engine shop and scanned his big '73-'91 trw book the 3000 series is, as i recalled, cast. forgings are in the 2000 series. to wit, all 3.750" bore, 0.931" wristpin: L3000F 'steel strut' 1.581" ch flattop [199] L3101F 'braced' 1.581" ch .118" cup 232/258 to '76 L3102F 'steel strut' 1.581" ch .134" dish 232/258 '77-9 L3104F 'steel strut 1.581" ch .140" valve reliefs 304 L3103F 'steel strut' 1.633" ch .158" dish 258 '80-'90 L2340F 'powerforged' 1.598" ch flattop [290] L2341F 'powerforged' 1.598" ch .108" cup ? L2360F 'powerforged' 1.598" ch .127" cup ? L2480F 'powerforged' 1.598" ch .140" cup ? so the 3103 is an '80s stock replacement cast 258 piston. and yes, that's what the 3104 description maps out to. maybe they mean .140" cup with valve reliefs as well? i thought no 304 slugs were flattops, though the hi-comp 290s were. and btw the cups above are flat bottomed; dishes are concave. ________________________________________________________________________ Andrew Hay the genius nature internet rambler is to see what all have seen adh@xxxxxxxxxxxxxxxxx and think what none thought