I can't answer what type of fuel injectors are used, but will ask. I have reviewed the RED documents, and they do not say.
As for the balance of the Beaver, it's actually better with the diesel installation. The Beaver was initially envisioned as using the Gipsy Queen engine:
(credit AOPA Pilot, April 1988)
The choice of the P&W R985 was made wisely, but perhaps too hastily. It was positioned too far aft on the airframe. The result was that original Beavers tended to be too far aft C of G. This has been a particular problem when on floats. I was involved in the test flying and approval of the modification to move the engine 9 3/4" further forward on the airframe, which moved the C of G forward, and allowed carrying a proper load in the back. I did very detailed W&B analysis on that configuration, including every plausible loading configuration. That understanding of the too far aft characteristics of the Beaver gave me great confidence in this new installation. Though the RED A-03 is heavier than the R-985, the MT prop is much lighter. The net difference is about 150 pounds heavier, at a slightly more forward fuselage station. This put the Empty C of G just where it needs to be for the Beaver.
I have flown the first diesel Beaver with full fuel, the boss in the right seat, and three 45 gallon barrels of water in the main cabin - still climbing at 600 FPM through 16,000 feet. The plane handled perfectly fine.
On the other hand, the Turbo Beaver does have a fuselage plug at the cockpit, as although the engine is placed well forward, it is also much lighter, so the fuselage had to be lengthened to maintain the correct C of G range.