Y engines starting with the ’58 models will have posted heads.  1957 was the last year for any non-posted heads being used for production purposes.  As far as exactly which heads are being used, the head casting numbers will need to be scrutinized as I've seen marine engines with a variety of different valve and combustion chamber sizes.

Lorena, Texas (South of Waco)

How long a period of time did they build the 312 marine engines?

Oldmics

The reverse rotation was only available in dual engine setups and in those cases, only one engine was reverse rotation to counteract the torque of the other engine.  Most of the core parts for the marine engine such as the short block and cylinder heads are interchangable with the car stuff.  The oil pan, timing cover, crank pulley and some miscellaneous parts were marine specific but many of the other parts are usable otherwise.

Lorena, Texas (South of Waco)

http://www.tradingdock.org/1864

http://www.marineengine.com/boat-forum/forumdisplay.php?f=13

http://www.dragtimes.com/parts/FORD-Y-BLOCK-272-292-312-RAT-ROD-MARINE-INTERCEPTOR_380215441773.html

http://mycars.home.comcast.net/~mycars/JetBoat/Instruction-Manual.pdf

 Seppo from Järvenpää, Finland
www.hollowheads.net (just click the hole in the head to proceed)

What parts can I use for an engine that I will build to race?

I think they are reverse rotation so the cam stuff is not useable.

What about the heads?Do they have some wierd cooling  plumbing?Would the heads be useable?

I assume block and crank would be keepers?

Oldmics