What FE and RE motor parts are interchangeable?

Gooday All,
planning my next project, which is an 84 RE which I hope to fit FE bodywork to, (cause I haven’t got R).
I’m not certain of the internal state of the RE motor, but have a very good FE spare motor.
Can anyone confirm:
Motor bottom end the same except for crank with gear drive? Obviously the cams, and gear drive assembly is unique.
What gives the R the slightly higher compression, piston shape, head thickness, or combustion chamber shape?
Are the rockers and shafts interchangeable?
I’m assuming con rods would be the same, but differing with the colour matching of the bearing shells?
If at least some of the bits will fit the RE then I’ll hang onto them I reckon?
Thanks in advance gents, and who knows, maybe we have a lady or two on the forum?

con rods are different as are the pistons and heads.
larger piston crown and altered combustion chamber shape give the extra compression

You can find the parts (nr) at www.cmsnl.com to see if they are the same.

Rule of thumb: If it has MB6 on them they should be the same. MJ4 is unique for “R”

Crank cases are different too. They have holes for the cam gear cassette retention bolts.

Thanks Gents, great information, so:

  • Heads, pistons and rods are definitely different parts, thanks @Bif

  • Crankcases are definitely different, thanks @Faxe

  • Parts in Common should have MB6 prefix, MJ6 unique for the “R” thanks @thx113

Appreciate your help, now I have to collect the bike, and see what I can start building out of what it really is- a 84 roller with motor and CB 1000 F wheels and forks, and what I have, lots of FE, and FF bits, and some R parts.
If I can, I`d like to run the CB 17" wheels, and go with FE bodywork if I can get it to fit? Not sure how side panels and tail will work out?..Luckily I have subframes to suit most of the combinations. Might be a bit weird position with the R rearsets, and F bars also?

There are differences in the gearbox as well because the selector drum turns in opposite directions between the F & R.

Gooday @DonR , I’m pretty sure that is positional- because the R has the single piece lever facing rearwards, versus the F with the linkage. From my race experience of the linkage types, reversing the linkage arm on the selector shaft, (e.g. from on top to underneath), would give you the reverse shift pattern.
I could be wrong however, never having worked on an R…

As far as I know, shifting up on the F turns the shift shaft clockwise and anticlockwise on the R