The Morgan Engine is the post x-flow engine from the Fiesta XR2. It uses a custom flywheel to turn the engine through 90degrees and mate to a Type-9 5 speed sierra box.

The architecture of the 1600cc CVH stayed pretty much the same, with only ancilliary changes to support injection and fully electronic ignition control.

the Cylinder heads are interchangable from newer-older on the blocks. There were several variants of Cylinderhead. The original Pre 86 casting 81SM6090 regular and Cross Hatched homologation version with slightly better inlet port flow shape. There are also later carb heads which slightly altered the dish of the valve area to a kidney shape(lean burn) which has problems with valve shrouding against the cylinder wall as well as the moulded insert.

Injection cylinderheads also have injector recesses cut into the inlet port which mean they are not ideal for carb use.

Quoted from Puma Race engines:

The primary identification without taking the engine apart is to go by the casting number on the inlet port side of the cylinder head. The first two digits indicate the design year of the head.

81SM6090 - pre 1986 hemi head (1600 Escort, Fiesta XR2, Bosch K XR3i etc)
There are two variants of this head. The standard casting and the rare cross-hatch casting. The standard casting has a plain flat finish to the external sides of the head. It's a good head for standard or 43.5mm valves. The cross-hatch casting has a ribbed cross-hatch pattern on the external sides and has thicker port walls and a better port shape. Only the cross-hatch casting can be used for 45mm valves.
86SM6090 - Lean burn head on post 1986 carb engined models.
88SM6090 - Generally these are hemi heads on the few carb engines that didn't go to leanburn in 1986 (Some Escorts/Orions I think) but see below. Essentially similar to the 81SM head but fairly rare to find one. I suspect the only intended difference is they'll have seat inserts fitted designed specifically for unleaded fuel. However, they also tend to have very bad port shapes and can't be modified for good flow or you'll break into a waterway. Best avoided even for ported standard valve work and absolutely no good for big valves.
88SM6090 - Just to confuse things some of the 88SM heads are leanburn although I've only come across a couple in 15 years.
89SM6090 - The EFi hemi head from Bosch L Fiesta XR2i's and XR3i's. Also has the injector cutouts in the inlet ports and therefore won't take a DCOE manifold without welding or other tinkering. Good head for big valves though as the port walls are very thick and the port shapes are excellent for flow.

End Quote

The RS Turbo engine obviously has lower compression pistons and usefully a dowled crank for mounting the Flywheel.

From what I remember the XR3 was an injected engine, so the bottom-end, crank, pistons & rods are the same.. only the head will have been the Injected version... these were fitted on post 85 Morgan 4/4's

Full link to Puma Race engines CVH article here:
http://www.pumaracing.co.uk/CVH.htm