It is true David, But it is also necessary to change the pistons. The relief area cut into the top of the pistons to prevent piston/valve interference is located slightly differently. Almost everything above the cylinder block has to be changed. ie. heads, rocker systems, push rods, exhaust manifolds, and rocker covers. In most cases the intake manifolds can be interchanged, but i'm a little uncertain of details after '56. Pre-'55 won't work (they are wet). Hot heads says that cylinder head locator dowels were enlarged slightly for '56, so depending on the years of parts being used that can be an issue. Hot heads can provide shouldered dowels so the conversion can be made without drilling. I have 2 C300 engines that I built largely from 2 301 poly engines that had freeze damage to the blocks and from abandoned 331 C300 blocks. Both blocks still had original 331 solid lifter camshafts, I purchased hemi heads ('55), non adjustable rocker sets, New Yorker rocker covers, original C300 intake manifolds and hemi exhaust manifolds. I was also able to find two pairs of original '55/early '56 carburetors. Main bearing caps, connecting rods, oil pump, oil pan, timing components and cover, water pump, fuel pump, distributor, dipstick and tube, and valley cover came from 301 poly. New egge pistons, new piston rings, new main and rod bearings, new camshaft bearings, new solid lifters, new adjustable push rods, and a full set of new gaskets for the '55 hemi all came mostly from Hot Heads. A good valve job on already good '55 heads topped it off. Gee, Have I forgotten anything? It was a fun project to preserve what I feel are very valuable parts. These two engines are fully operational and I run them on a regular basis to assure that they are well preserved. I'm uncertain of block design details of the '57 and '58 354 poly blocks. The '55 and '56 engines shared a 2 year only water pump design. What I don't know for certain is whether or not there is a difference in the timing cover and whether or not the older water pump design can be fit to the later block. I will guess that it can. Someone please tell me if that's not correct. I'm curious. -------------Marshall Goodknight 3NE551536 AND 3NE552113 ____________________________________________________________ You'll Never Think About Solar Panels After Seeing This Patriot Wealth http://thirdpartyoffers.juno.com/TGL3131/5b761b13894871b1357b2st04duc [Non-text portions of this message have been removed] ------------------------------------ Posted by: "mgoodknight@xxxxxxxx" <mgoodknight@xxxxxxxx> ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to https://groups.yahoo.com/neo/groups/all/manage/edit For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang ------------------------------------ Yahoo Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: Chrysler300-digest@xxxxxxxxxxxxxxx Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo Groups is subject to: https://info.yahoo.com/legal/us/yahoo/utos/terms/