differences - 79 to 82 258's

I MAY have to make a decision on the SX/4.
It's an 82.
I have this engine I got from Edelbrock that's a brand new 1979 258, never been in a car, probably the equiv of about 10 miles on it, tops.
I can't put the 79 in an Eagle due to lack of casting to support front differential of the Eagle.
I mean, for all practical purposes, this thing is factory new, except for the work they did - shot peening, balancing, etc. If that block had the differential support casting, I'd be putting that engine in there today.

Some thoughts are - obtain a 1980+ 258 block, have it blueprinted and put the guts from the '79 engine in it, head and all, so I have the better valve cover.

What are differences in the heads, cranks and other items that might preclude me from doing a simple swap of guts from the 79 to, say, an 81 or 82 block?

I'd like to build any engine, and have it ready, and then simply pull this one and drop in the new one in a day - IF it comes to that. If the oil pressure comes back on the SX/4, then it will be a "someday" thing, but I still want to plan for it, so need to know what heads fit what, and design changes to the 258 from 79 to 80, 81, or 82.

Facts, please.......
For example, I know the 79 and 80 had the good steel valve cover that bolted on, and the 82 had the plastic one held on with studs, but what where the other changes?

I also have a comment to make as well.................now, I'm the worlds worst when it come to these 6 cylinders......I have a 1981 & 1983 258's   and they have the Plastic valve cover,    IIRC, 1981 is the year AMC changed the # of weights on the crankshaft on SOME of these engines......some early 1981 engines were the Heavy engines and some of the later 1981's were the "lighter" engines........?   is this right or this is nonsense?

The official change over to the lighter cranks happened in '81.  But, we all know some of the heavier ones could have been used in '81. 

An aside, I wonder if AMC supplied heavier ones to persons replacing pre '81 cranks.  Or if they just shipped out the lighter style?

If they changed cranks, would they not need rebalanced?

gaskets are different detween steel cover and plastic will not interchange    i don't think    didn't the last years or so of the eagle have a factory aluminum cover ???  me and my brother tried an older cover on the newer engine they did not match up   he had an 81 sx4

Edited by matty 401 - Aug/04/2007 at 1:11am