Hi Purs,
You need to stay with the same crankshaft size, otherwise you will encounter serious deck drive belt alignment, a new clutch and drive unit pulley.
The muffler will line up directly.
The engine control cables will connect with no problem. Fuel line and starter motor electrical cable should be a direct fit.
The Briggs engine harness connector should be the same 6 pin connector, you will need to check to make sure that the terminals in the engine connector line up with the terminals in the machine harness connector. Only 3 of the 6 slots have terminals, you may need to relocate a terminal or two.
I strongly recommend that when you have the old engine off, that you replace the ring terminals on the ground wires that are on one of the engine mounting bolts.
The controls for the choke and throttle on the new engine have a shorter throw than the old engine has. What this means is that the choke and throttle levers
will not move as far to accomplish the same effect on the engine.
I repowered my Tiger Cub in March 2012 and having had problems with the original and 2nd Scag hourmeters, I now have an analog hourmeter.
My new engine has at least 300 hours, possibly 400 hours having had the hourmeter problems.
The Commercial Turf engine has the Cyclonic Air filtration System which I have found to be very satisfactory in dusty conditions. This engine also has a cast aluminum intake manifold whereas the other Briggs models have a plastic intake manifold which I'm not crazy about.
These engines come with an engine oil cooler and a much increased cooling system.
As I have said, I'm pleased with this engine and this is the least expensive way to repower an original Briggs Intek, ELS twin.
I also have a 2012 Hustler X-ONE with a Kawasaki FX730V engine, definitely a sweet engine and I was set on repowering my Tiger Cub with a Kawi until I priced what I needed to make the conversion. Kawasaki doesn't make mufflers, Briggs does, so I would have needed to order a muffler which wasn't available at the time. The Kawasaki price total was more than twice the Briggs engine which was $850 delivered at the time. Prices have gone up!!!
Scag has manuals available on their website. Post the model and serial number range of you Freedom Z so I can look at the parts manual for your machine and possibly further assist you should you decide on the Briggs Commercial Turf engine. The HP that you decide on, 25 or 27 really doesn't make a lot of difference, the crankshaft size does.