That is part of it. The Autobianchi engine is 600 based which was CW rotation. You will also need to flip the pistons around the opposite way, get a 903 oil pump, water pump, alternator and change to a different gear set to run the cam I believe.
The Abarth block is based on the Fiat 127 block, different water pump mounting pattern, has a screw on oil filter (no centrifuge) and is set up for FWD.
You don't spin the pistons (surprisingly) as the offset for an 850 CCW engine is actually incorrect... I know I know... but look closely and the 127 engine (CW) and the 850/903 (CCW) pstons are interchangeable as the 850 was actually offset the "wrong" way...
The oil pump always spins in the same direction in both CW and CCW engines, same with the distributor... always turns clockwise...the difference is the cut on the gear for the oil pump drive jack shaft so you need the correct jack shaft for CW or CCW rotation respectively. Camshaft is different, so you need to use a CW/CCW lobe in the correct way... OR... use a set of cam drive gears to reverse the rotation of the cam, now these are not gears with a chain connecting then (both shafts turn in the same direction) they are helical/or straight cut gears that are in mesh (shafts then spin in opposite directions)
Gear set for cam/crank when using a chain is the same ...what is different is the timing chain, this is specific for CW and CCW rotation, as the little "slingers" on the chain are offset to suit rotation... use the wrong chain and you'll have an awful racket from the chain!
Alternators can be spun both ways and still work...the difference is the lay of the cooling fan fins.
The number one simplest (and by far cheapest) way to increase the engine capacity to 965cc or larger is to offset bore the block and use 67.2 pistons from an Autobianchi A112 elite (not abarth) This engine still uses the same stroke crank as the 903, it still uses the same press fit gudgeon pin conrods as the 903, all that changes is the size of the piston.
The 1050 engine is a different crank, very different conrods which are lighter and have the small end bushed, full floating gudgeon pins, pistons to suit the FFG with grooves for pin clips and a shorter deck height to the piston to suit the longer crank stroke
SteveC