Incase it is worth elaborating, according to my Pete McCarthy book here the secondary stampings used on 1973-4X heads are:
1H (455) 114cc or 112cc
3H (400-4bbl) 98cc
4H (400-2bbl*) 98cc
7H (400-4bbl) 98cc
I know this reference source has some errors - I have a page that Mr McCarthy compiled about 1973/1974 engines somewhere here...
*According to Pete's book, the 4H was only on 2bbl motors, and my guess was that these were small valve heads;
I decided to investigate further, and went over to John's site - and sure enough, it indicates that the 4H was a small valve head;
Johns site also suggests that some of the secondary stampings were missing the letter code - so "3H" could have been stamped as "3" - ditto on the other secondary stampings.
Pete's book also suggests that the "3H" stamping was only used on manual transmission engines - while "7H" was used on automatic engines, and if Pontiac engines from a couple years earlier are any indicator, maybe there is a combustion chamber difference between the two??
http://www.wallaceracing.com/headsearch.htm